DH secretly reconnected with ex GF

Are any of the messages of a flirty or sexual nature?

Not being rude to your husband but has he let himself go and is excited about someone who used to find him attractive taking an interest in him?

It definitely is unfair of him to be having friendly chats with her and you not knowing even if the chats w innocuous. He may well be reading things into it.

He likes her attention, that's for sure.

Yep! Agree with everyone else. You need to start a general friendly conversation about the reunion. Act interested, and then ask who is going and wait for him to hopefully offer up the information that she will be there.

Would there be any other reason for keeping the fact she will be there from you? For example does he think you will kick off? Have you ever been jealous or unreasonable about his ex's before? If so that might be a reason he won't mention her, because he is scared of the drama it might cause. Not that this is an excuse of course, but it might explain things a little.

However if this is not the case and you have never shown any jealousy or kicked off before then its really unreasonable for him to keep it from you that she will be there and I would be wondering why he hasn't told you. I would be wondering what he was trying to hide and why he was not being honest about it.

I hope it goes well and I totally understand you feeling uneasy about this.

Has he given you reason to be so untrusting and suspicious of him talking to someone he dated over 20 years ago before he met, fell in love with, and married you???

I know 3 people whose DHs reconnected with their old girlfriends in similar circumstances and all 3 had affairs with them. It seems that it reignited their sense of being young and in carefree love from all those years ago.

The advice from PPs is good. Trust your instincts when he responds to your questions.

Awww I can only imagine how you felt to find the message.
agree with above, start a general conversation and take it from there. I hope it goes well though.

I agree with pp that it's concerning he hasn't mentioned the messaging, as it has been going on for months and is quite frequent. He will already obviously be excited about the reunion with his Uni friends in general and the conversation he is having with his ex sounds as though it will be building up the anticipation of actually seeing her and making that alone into something special.

I also agree with pp about starting a general conversation about the proposed reunion and see what, if anything, he has to say about his ex being there. And there really does need to be a conversation with him about his ex, the messaging, and his feelings.
Also a conversation about maintaining boundaries as a married man in a loving relationship and respect for his partner.

This is really difficult, I can absolutely understand your concern here..
I think firstly ask him for specific names of who will be at this reunion, and see if he mentions her name. If he doesn't, then that definitely is a bit suspicious especially if they've been messaging secretly for months. If he's open about it and says she will be there, and is happy to talk about your concerns and reassure you, then maybe it is innocent. But it doesn't look good when he hasn't mentioned he's been speaking to her. Are there definitely others planning on meeting too? Have you seen the messages to his other uni friends about this reunion?
Ask him who's going, if he mentions her name, ask how he knows that and if he's been speaking to her too. If he doesn't come out with the truth about her being there and messaging her, I think you may have to come clean that you seen the messages and question why he has lied to you. It all depends really on how open and honest with you he is when you ask him for more information.
Even if he is honest when asked, if you're not comfortable with him staying overnight knowing she is there, then that needs to be discussed too.
Good luck x