DH and his friend

I think the fact that he's not on the phone to her at weekends kinda proves that this is a work support thing.

Honestly OP I think you're being a bit ridiculous here, is this the first time he's had a female friend?!

Sound advice.

Wow, because he talks to a colleague about work stuff that is quite the leap!

Oh please!

The fact you are feeling uncomfortable about it is really all that matters op.
It may well be entirely innocent but if its encroaching on your relationship then boundaries need to be set.
It's perfectly reasonable to expect that his friendship with another woman doesn't intrude on your time together as a couple or family time. It's also perfectly reasonable to ask he doesn't discuss anything to personal with her, especially your relationship.
Emotional, and subsequently physical affairs often start with friendships, which start to encroach on the primary relationship. What then happens is connection is slowly lost from the primary relationship as its being fed into the friendship. You then get frustrated, leading to him complaining to his friend and the scales tip away from you.
Of course men and women can be friends but you both have to determine what boundaries need to be there so you both get both the freedom and the safety you need.

TBF this could 100% describe my job. Every day. Multiple times a day. It's hugely stressful. People trying to land grab, power grab, backstab, plus drama with direct reports, plus context of the actual work itself being stressful. Only you know if your husband's job is a bit like this. I'm just mentioning it as jobs like this do exist.

Your relationship is done. There’s only so much room in someone head for a romantic connection. He’s dedicating his thoughts and his space in his head to her. You are no longer his priority. If he hasn’t already slept with her, he probably soon will.

If you’re not his primary concern then there’s an issue. Obviously they will talk a lot, message etc if they are working together but that shouldn’t cross over excessively into personal life unless you are both happy with it.
we need to be able to switch off from work and it doesn’t sound like the friendship is allowing him to do that as much as he should.
I also do wonder if you need to allow him to decompress with you about his working day. He may need the decompression and in the absence of you, he’s using her.
I think you need to sit down and talk about the time spent with this friendship eating into your time.

Sounds like an emotional affair to me.

What is ok in your marriage is not ok in a lot of people's marriage.

When someone marries they usually expect their spouse to be their primary relationship. In OP 's case it appears she is no longer her H's primary relationship because otherwise he wouldn't be messaging another woman at 6 a.m in the morning when OP had every right to think that she, and his home life was uppermost in his thoughts. Not his woman colleague.

Of course it's ok to have friends of either sex. But not when the friendship intrudes into the relationship between man and wife.

The drama can be an excuse? Like every week there is some kind of drama? Someone is ramping this up. Nope. Not ok.

Trust your instincts here OP. Sorry to hear this - it sounds like you are sensing something he may not even be consciously aware of. This is an OTT level of contact. I had this and I sat on my feelings or was gaslit and it ended up nearly breaking my marriage and family and honestly my own mental health. Nip this in the bud now - its unacceptable behaviour and it needs to stop.

He’s already cheated on you and left you in his head. If he hasn’t already left you physically, it won’t be long.

Honestly, this feels like it's a you problem. He's in a high stress situation at work and is communicating with a colleague about it. Have you seriously never leant on a co-worker during a stressful situation? Have you really never been in a work situation that became the whole focus of your life for a bit? If so, I'm jealous, and want to know what your career is!

You've read the messages (which seems weird to me, does he know you've done that?) and you admit there's nothing weird going on. You also admit that you're not interested in talking to him about it.

To me, it sounds like you're being insecure, either about your relationship with him, or about your ability to match him in terms of understanding.

Of course most people wouldn't be happy with this!
Speak to him, bring it out in the open and hope your fears don't come true.
All the best x

Anyone ranting about work all the time would be dull. What's the context for how he frames the colleague. Is it 'it was so great when she did XYZ' or is it 'we had to go into a meeting and land some points about ABC'

The former = possibly worrying if it's all the time, the latter would be dull for you (but possibly good that he has support in a stressful role)?

Ok but if you can't be bothered to listen to him talk about it, I don't see how you can be upset that he's talking to someone else about it?

Is he telling you about his work constantly, or about the woman constantly?