feel like DP is up to something & want to catch him out

[BigSquareShoe]

I'll keep this as brief as possible.
Been with DP 20 years, 1 primary age DC. He has returned home from working abroad & something feels 'off'. We haven't had sex in over 3 weeks now, we actually sit in separate rooms most of the time & have very little to say to eachother as he is constantly on his phone. It was our DC's birthday last month & he left the room midway through gifts and went to bed without saying a word.
I have discovered he has been 'liking' photos of women we both know on social media, a lot of them. Which I am mortified about but don't want to seem controlling. He also recently let slip he has 'Snapchat' which I see no reason for a grown man to download at this stage in his life. Basically it feels like we are living separate lives & I can't get past the hurt I feel over these things. I need to get actual proof of wrongdoing which is going to be difficult as he is on his phone 24/7. He basically has no interest in family life or me & we haven't gone on a date night for at least a year if not more. This isn't a post about leaving him, I want to know how to catch him out.

And if he's not cheating?

I don't want revenge. Or to have the moral high ground. I just want to know I tried my best, that it was taken out of my hands. I suppose that's a cowards way out & I envy strong women who can just walk away from relationships that are clearly over. I feel the disruption to DC's life would be too much to justify doing that, without knowing a line had been crossed. He knows my feelings on cheating. I'm pretty relaxed in other ways & it's making me feel uneasy that I'm so consumed by the thoughts of this. But something is 'off'. I'm not gaslighting him, unsure why that's a suggestion. Ultimately we can't carry on as we are but I know if I confront him without proof he will make me out to be crazy & I'll start to believe it. I don't know why I need proof in order to leave. Maybe it stems from childhood issues. I wish for nothing more than us to be happy. Sadly I think any chance of that is long gone.

You've been together for 20 years, can you not just talk to him and ask directly is it over? You don't need proof, because it doesn't make any difference.
You aren't a child any more its time you approached this like an adult.

@Gettingbysomehow - excellent post!

Our very long marriage (not all hearts and flowers) has been filled with conversations. Not confrontations. If one of us feels something is off then they raise it with the other. We have a conversation, make a plan and things get better. Why does there always have to be another woman (or even a man)? He may just be struggling to reintegrate himself into family life after being abroad and your attitude (which is probably being packed up by him and your DC) won't be helping. You need to talk. If he can't reassure you then you know its over but you may have just grown apart during the last few years rather than something more sinister and you won't know unless you talk to him....

Haven't RTFT. You'll need to either get hold if his phone (even then he may delete everything) or follow him. If your gut says something is going on then it probably is, but if you can't get proof then of course you'll need ro speak with him

If you cant prove anything, then what? Do you stay, feeling unhappy?

I get the sense that if you arrange a babysitter for DC for a weekend and sit him down and tell him calmly that you arent happy and open up a conversation asking how he feels and where he thinks things are going, I think you'll be surprised and he will agree with you and hopefully that your sign that its time to finish things. He sounds more checked out than like he is "just" cheating or having sex.

I get the wanting proof, I do I just dont think it will be the satisfying gotcha moment you're hoping for. How things end will really set the tone for the separation. Better to have a respectful conversation than angry tears.

I think everyone saying have a conversation with him etc means well but doesn't understand the kind of person I'm dealing with. Thank you for all the helpful suggestions & advice, I have read and appreciate every single one.

If you are really determined to find out then I would recommend hiring a private detective. Ideally you could just get an air tag or something similar but if it's likely he would find it in his bag then that's no good. I was in this position when there was less technology and I really wish I had taken action.