Assume there is an affair. Now what does that change for you? In reality not much. Bust at least if you take it as being true, maybe you can stop wondering and hence dwelling on it. Easy to say but not to do.

My advice to you is to concentrate on sorting your issues out first. You are broken. In that state you are unlikely to fix anything else. And if she did come back, you are not in a position to build a new R. I am blunt but do so with your best interest in mind.

I will repeat a slogan that is doing the rounds on internet: it's okay to not be okay.But no doctor or medicine can change that unless you are ready for it to change.

This is a tough time. The good folk here can help you through it.

Best wishes

R 25 years
M 14 years
S11 & S13
Working on it alone since Oct 2014
M in trouble a lot earlier (~2 years)
Feb 2016. 1st R chat in a yr.
Next R chat Aug'17
Still together