Need advice. Getting over betrayal?

L

My husband and I recently went through a rough patch in which he was unfaithful to me. All the trust I had in him is gone. I don’t trust him one single ounce, but I {hope} it was just a mistake, he was sorry and we decided to work on our marriage as long as he changes. But since deciding to work it out I am like OBSESSING over him... I can’t stop thinking about what he’s doing, what he’s thinking, if he’s noticing other women, if he notices me etc. We have friends who we hang out with often and we were talking about going to the beach soon. The wife of that couple is drop dead gorgeous (and I already know my husband thinks so too) and I literally don’t want to go to the beach with our friends just because I don’t want him looking at her in a bathing suit. What the f am I crazy? I know I have a right to not trust him, and trust grows slowly. But how do I still have fun and be happy and not obsess over this???