How do I stop being so paranoid?

Me and my boyfriend have been together 8 months. We met over a year ago and he cheated on his girlfriend with me and other girls and denied it. A lot of rumors start that he cheats on me, but its impossible. I'm with him literally every day. We live a block away from each other. We tell each other literally everything no matter how much it hurts. I even told him that I cheated on him. It resulted in a fight but he was glad I was honest. I trust him, I do and he never hurt me while we were together. He does EVERYTHING for me. But whenever rumors start, I doubt him even though I believe him. I guess I'm too scared of being hurt by him again. How do I stop being so paranoid and stop having trust issues?