I'm in a relatively new relationship and cannot control my anxiety from past relationships.

I'm in a relatively new relationship, which is the best I've ever had. I've been cheated on by every other bf I've had (3 to be exact) and cannot help but nearly 'look' for problems. I've explained to my bf and he is super understanding, but I'm afraid that I'll ruin it completely. I attended regular therapy, but I'm just terrified that he'll get fed up with it, and me, and it will be a repeat cycle