Am I crazy?

So, i have been with my SO for a year and a half, and I am definitely still scared of the what if’s. ‘What if he cheats’ ‘what if he is talking to another girl’ given that my last couple SO’s have been very unfaithful. One I actually caught in his room fucking another girl when he was supposed to take me on a date. Honestly, I trust my current SO completely because he has had similar problems. His last gf he proposed to, she said yes, and then she cheated on him 3 days later. I always want to check his phone even though I know for a fact that I won’t find anything. We both have the same password and we both play around on each other’s phones anyways. So it’s not like he would get mad if I did. We promised each other that if at any point we felt we needed to check the others phone, we could. I just feel like I’m crazy for feeling like I have to even though I know I won’t find anything. HELP ME AND TELL ME IF I’M CRAZY