Sounds like you are pushing buttons and accusing him of things he has not done. You pushed him so far he finally said look, if I was going to sleep with others I had the opportunity to do so, and I didn’t. You continued to push the issue so now he’s trying to prove to you , you have no reason to be so suspicious. He’s giving you chances to see he hasn’t done anything. Instead you are make an issue out of it. You need to see a therapist and work on your trust issues. Tell him lovingly that he no longer needs to prove anything to you. That you are going to step up and be accountable for your lack of trust by seeing someone for it.