I have been in your shoes. I think a good deal of your struggle might have to do with control. To me, control issues and anxiety go hand in hand. I had my own epiphany when I realized that no amount of hand-wringing would cause my husband to not stray, or to stray. The choice was all his. I had NO control. Not having control is a huge relief, in many ways, because with control comes responsibility. How could you be responsible for someone else's actions? You can't.

And beyond that, I told myself that no matter what he did, be it stay faithful, or stray, I was going to be okay, NO MATTER WHAT.

Between those two things...recognizing that I did not have control, and recognizing that his actions did not change who I was as a person, that I was good and worthy no matter what, I was able to let go of a great deal of my anxiety.