I don't have any advice really. :( I have found that over time, I have stopped obsessing and wondering. (Maybe I got too many details oops.) Horrible answer, right? Time -- there's absolutely nothing you can do to speed it up.
I have found too that working on re-building my self-concept and self-esteem has helped. I've been going to the library, learning new things, excelling in school, etc., and that has given me something else to focus on, since in the end, we can't really control whether or not they choose to tell us the truth.
I know exactly how you feel. You ask does it ever stop or get easier? Honestly I can't tell you because I wasn't about to stick around long enough with my now x-wife to find out.
But I can only guess that it does get easier, but IMO it will never go away. Which is why I divorced her. I wasn't wanting a life of being even the slightest bit suspicious, no matter how few and far between it might have been.
So the question is, are you willing to just accept it? Because honestly, thats all you can do. And if you aren't willing to accept it, are you prepared to change your life for the better? Find someone better?
Gosh does it ever stop or get easier?
As it progressed, I learned that my defense mechanism was to automatically believe nothing and assume the worse. Eventually I seen that was an inaccurate assessment of her behavior that only drove me crazy. There were (are) moments that would send me into instant full on suspicion, but they are becoming fewer and farther between and much less intense. When you are ready, you can let your WS know what it is that causes you distrust. That helped me (it didn't fix it, but it helped).
I think I got to the point where I just don't give a shit anymore because it doesn't do me any good to be suspicious without evidence. There are still those "trust your gut red flag moments" that you certainly cannot rugsweep, but some of the worry was unfounded and just makes you sick for no good reason.
If your WS is willing to do the work and you want to consider R, then it is acceptable to give them a road map of sorts to get their general direction set. Once the initial shock of d-day wears off, you'll be in much better shape to analyze the suspicion. In my case I am taking a little too long, retracted my commitment to R and am in limbo somewhere between R & D.
I always hated the expression "trust but verify" because it was devoid of the instant gratification I was seeking. But, it is good that you notice what is happening. You are just spooked at every little sound in the jungle of infidelity. Sooner or later you'll learn what is ok and what is not.
I hope you find your peace soon.
If he says he will...go through with it. A lot of the time they will agree,thinking you will back down.
..that feeling you get in your stomach, when you heart's broken. It's like all the butterflies just died.