AIBU to install cameras because I suspect my husband is hiding affair?

I think this is really good advice.
IF and only IF you do still want a future with him may I also suggest:

Yes proactive rather than reactive 100%
Come down hard NOW, it’s the only way you will be sure he cuts off all contact, and cut off ALL contact is absolutely necessary.
He gives you access / and Face ID to ALL his accounts. He will agree if he wants to stay married to you.
He agrees that he will never ever contact her again.
He tells you everything and gives you access now (b4 he deletes everything)
CONTACT HER HUSBAND - don’t tell yours that you are doing this, you may well learn more about what’s been going on and (assuming you are still wanting to stay with him) when the sh@T hits the fan from both partners, their cosy little togethers and their relationship won’t seem at all exciting anymore.
You say the OW is married and won’t want to blow up 30+ years - then she shouldn’t have been in secret contact with another woman’s husband /her ex partner.

“you are always on my mind”
And more messages.
Did you meet up for lunch with his friend ?

Please take action and let him know you are not waiting around for him to “sort out his past”
I wish you all the best 🌺

Has he explained what "sorting out the past" actually involves?

Assuming you want to save your marriage, rather than just walk away, I think your H needs to be crystal clear about what is actually going on with this woman. Is it an emotional affair, has it become physical, what are his feelings for her?

Of course as he has already lied to you and continues to lie regarding what is going on, I doubt you you can rely on much that he says. Only you can know if the trust is gone permanently.

I think you need to somehow take back control of this situation and become proactive rather than reactive. Is there somewhere you can go for a few weeks to consider your future and what you want? I'd tell him that I could not bear to be around him when he shows me no respect, lies to my face and totally disregards my feelings and then leave him to try and find a way back from this mess of his own creation. Perhaps this is the wake up call he needs.

You need to decide if you actually still even want a future with him or not.

The expression I find extremely odd is
" lunch arranged for next week with husband & his friend & me" In my head I am imagining you saying darling if you and...... are arranging a lunch date do you mind if I join you both.

If my husband arranged a social lunch date with another woman I doubt I'd be joining them. I wouldn't stick around to be part of that situation. As married couples we all have our own particular bounderies & for me this scenario crosses the line.

Thank you for all who have replied,
Someone said ‘what do you hope to get from your post’?
My answer is others points of views and thoughts.
This is an on going and live situation.
Lunch is arranged for next week with my husband and his friend. And me.

Life really feels weird right now. And I am thinking it through.
I really appreciate people’s thoughts about this. I am trying to stay even emotionally about this.
I suspect I am not the only person that is finding this odd.

Thank you for all who have replied,
Someone said ‘what do you hope to get from your post’?
My answer is others points of views and thoughts.
This is an on going and live situation.
Lunch is arranged for next week with my husband and his friend. And me.

Life really feels weird right now. And I am thinking it through.
I really appreciate people’s thoughts about this. I am trying to stay even emotionally about this.
I suspect I am not the only person that is finding this odd.

Thank you for all who have replied,
Someone said ‘what do you hope to get from your post’?
My answer is others points of views and thoughts.
This is an on going and live situation.
Lunch is arranged for next week with my husband and his friend. And me.

Life really feels weird right now. And I am thinking it through.
I really appreciate people’s thoughts about this. I am trying to stay even emotionally about this.
I suspect I am not the only person that is finding this odd.

Thank you for all who have replied,
Someone said ‘what do you hope to get from your post’?
My answer is others points of views and thoughts.
This is an on going and live situation.
Lunch is arranged for next week with my husband and his friend. And me.

Life really feels weird right now. And I am thinking it through.
I really appreciate people’s thoughts about this. I am trying to stay even emotionally about this.
I suspect I am not the only person that is finding this odd.

As I said in my post:
Yes, there is a high probability that, if there is anything but friendship with this woman that your H will lie.

I am not, and never will discount that people who cheat will lie and gaslight without a second thought. And they are willing to go to the extreme in order to be believed.

I can totally understand the need to have concrete proof of cheating, I’ve been on the receiving end and it’s an awful place to be.

But, this is a thirty year marriage that, from the information given by the OP, has otherwise been good.

I’m not saying she shouldn’t actively seek out proof, just that maybe a conversation with her H should factor into that somewhere.

All very good advice, except for:

"But just ask him. you don’t have to be accusatory, just say that you know the two of them have met up recently and that you feel it’s odd that it wasn’t on the calendar like his meet up with other friends are."

Cheaters are, by definition, liars. If you ask a cheater for the truth, they are going to LIE.

And their lies can be so astounding and flagrant that the betrayed spouse can start to disbelieve their own senses. I remember a few years ago, an OP came on a forum I was reading and said that she came home early one day; walked into her house; her H came bounding agitatedly towards her, shirtless and his hair dishevelled and saying he been napping; she saw movement in the bedroom behind him and started walking towards it; and her stark-naked neighbour came rushing past her, clutching her clothes to her chest, and vanished out of the front door.

And when OP overcame her speechless flabbergasted shock and started questioning, he said he was sick of her jealousy and the neighbour just came over to ask him to look at her toe, which she had jammed in a door.

And OP was so confused that she actually came to the forum to ask if she was unreasonable to doubt him!

Cheaters lie lie lie lie and lie. They've become the enemy, it is completely POINTLESS to ask them to tell the truth. They won't because that is partly WHY they cheat: they like lying and their lies.

I have zero problem with OP checking out what her H is doing. Cheating is abuse on many levels: mental, emotional, physical (STIs can be deadly), and above all financial. Marriage is a social contract: you need to protect yourself from partners who go bad and who can blow up your life.

And to the idealists on this thread saying, well, if you're checking him out, your relationship is dead anyway because you don't trust him: there is a LOT at stake, and NO ONE - including you - is going to willy-nilly blow up a decades-long relationship on the basis of an unconfirmed hunch.

This is dumb advice that does only hog-ties the victims of cheaters.

All very good advice, except for:

"But just ask him. you don’t have to be accusatory, just say that you know the two of them have met up recently and that you feel it’s odd that it wasn’t on the calendar like his meet up with other friends are."

Cheaters are, by definition, liars. If you ask a cheater for the truth, they are going to LIE.

And their lies can be so astounding and flagrant that the betrayed spouse can start to disbelieve their own senses. I remember a few years ago, an OP came on a forum I was reading and said that she came home early one day; walked into her house; her H came bounding agitatedly towards her, shirtless and his hair dishevelled and saying he been napping; she saw movement in the bedroom behind him and started walking towards it; and her stark-naked neighbour came rushing past her, clutching her clothes to her chest, and vanished out of the front door.

And when OP overcame her speechless flabbergasted shock and started questioning, he said he was sick of her jealousy and the neighbour just came over to ask him to look at her toe, which she had jammed in a door.

And OP was so confused that she actually came to the forum to ask if she was unreasonable to doubt him!

Cheaters lie lie lie lie and lie. They've become the enemy, it is completely POINTLESS to ask them to tell the truth. They won't because that is partly WHY they cheat: they like lying and their lies.

I have zero problem with OP checking out what her H is doing. Cheating is abuse on many levels: mental, emotional, physical (STIs can be deadly), and above all financial. Marriage is a social contract: you need to protect yourself from partners who go bad and who can blow up your life.

And to the idealists on this thread saying, well, if you're checking him out, your relationship is dead anyway because you don't trust him: there is a LOT at stake, and NO ONE - including you - is going to willy-nilly blow up a decades-long relationship on the basis of an unconfirmed hunch.

This is dumb advice that does only hog-ties the victims of cheaters.