"And I just know he will deny everything and make me feel like I'm going crazy unless I can say I've seen proof with my own eyes. I don't want him to be able to continue this while being even more careful because then ill be even more trapped in an impossible situation."
Eventually, after a long time, ab, you will see that this in itself is enough reason to take action. If you just know that that's kind of sad.
Do you want to be in a relationship with someone who will gaslight you like this, make you feel crazy, attack you and then carry on being unfaithful? I'm not saying you have to leave the relationship, I'm saying you need to CHANGE it. IF you really believe that is what will happen, and that you will just accept that, feeling thwarted, then why the hell carry on looking for evidence? You assume that you won't leave a man who lies, denies and bullies you about his own wrongdoing and then carries on doing it anyway, so where is your line?
I get it's hard.
And you are never trapped in an impossible situation. There is always action YOU can take. It's crazy that everything is framed from his perspective, you are obsessed with how much evidence you can amass that will prove TO HIM that he is having an affair. Think about this. This is insane. He KNOWS HE IS HAVING AN AFFAIR. HE SEES ALL THE TEXTS. It is YOU who must think about what you could see or read that will be enough for you, not him. It's almost as if you are waiting to find proof so that he can make the decision about what you should do. This weird focus on the cheater not being made to feel uncomfortable is bizarre. And it shows how deeply passive we can become in relationships where we fear loss.
You are so used to being bottom of this order and him being central that I don't think you can even see at the moment that there is a totally different way of seeing things. A way that is from your POV, not his, not a family member's or outsider's. Or on the other hand, there's a way where you are on the same side of this thing, being honest about the affair and then deciding what you both want to do, maturely, instead of indulging in stealth manoeuvres against each other. (seriously, he is deleting his texts, you are sneaking round checking them at night, you may as well be spies at war with each other.) It's amazing how many of us end up in relationships where we are essentially enemies with our partner (read the novel Gone Girl).
You're caught in the evidence trap, which is okay, you might find something that clarifies things for you. But I ask you to keep reminding yourself of these things.
- Your DH is very thorough. This implies he is good at covering tracks, possibly even practised at it. So the worse the evidence is, the more likely it is he will successfully hide it. You may never find it unless you step up your surveillance to another level. If you never do, what will you do? How long? A month? A year? I'm not being facetious. Decide. Write it down.
- If you step up your surveillance to another level, AND you discover something, then he might be so shocked at the lengths you went to that he tries to make it about you being crazy "You hired a private investigator!? You're crazy! I'm out of here" (or the classic, "You've now done just as much wrong as me, you've broken my trust!") What will you do then, think about it. Write it down.
- Most evidence will be explained away in the most minimised way possible by a clever cheater, as I said before. "Sex talk? It was just talk." "She fell in love with me, I was just trying to not be rude." "I knew you would react like this, so I deleted them."
- The situation may change as time goes on. Even if the affair stops somehow, in my experience, a large number of affairs are actually ended by the OW who gets sick of the lies and guilt. Then, if discovered, the DH pretends that they ended it to the DW, and 'chose' them, which emotionally suddenly they miraculously feel like they did, having been rejected by someone else. If you don't address this whilst it's happening you will never know any truth and spend your life not knowing what went on in your own marriage and not feeling able to ever ask.
Phew! That's it. Just plugging away to keep you from the tempting slow death that is denial.