Maybe this is a self-esteem issue. In a way you are sabotaging your relationship.

If you act normal, your boyfriend doesn't sound like he will ever cheat. But if you keep being very suspicious and insecure, he might in the future get fed up with the relationship, and move on or who knows even cheat.

Maybe deep down you feel you don't deserve your boyfriend and then sub-consciously start to sabotage the relationship?

If you don't mention anything about him cheating, I think your relationship has a better future. I think it's better to obsess a little but NOT make is verbal so keep it to yourself. Saying these things about cheating will maybe slowly drive your boyfriend away. If you can, keep it to yourself.

Maybe this is just a phase that will pass in the future. Relationships are full of phases. I hope things work out for you.