Feelings

My so left me a while back for someone else and maybe 1 month later realized he couldn't live w/o me and knows what a big mistake he made so I took him back. Now he has changed a lot and is trying his hardest to show me he truly loves and needs me. Thing is, I have horrible trust issues now with him. I've never cheated or done anything behind his back(which he did to me before he broke up with me). So when we weren't together I was hanging out with friends of mine and one guy (who's a friend) I'm really attracted to and I know he's attracted to me. Well when me and my bf got back together I cut off all ties with everyone outside of the relationship Bc I feel that's the adequate thing to do. This guy and I work together though and we've kinda started communicating again( on a friend level as it's always been) and I feel like I'm catching feelings for him. He makes me want to do things I've never done and i am extremely tempted. I normally wouldn't EVER think of things like this but ever since my bf did what he did I feel the need to do things out of spite. But on the other hand I never wanna cheat on my bf and I feel bad for having these thoughts. What would you do?