Boyfriend thinks I’m cheating idk what to do

So me and my SO we’ve been together for a little over 3 years and we were going to have sex last night but I’m ovulating so I wanted to use a condom, he goes to grab them and he counts them and asks me why there’s only 7 because there was 8. I said I didn’t know because I truly did not know. Come to find out he said he counted them last week and there was 8. So obviously I’m getting upset because he’s basically implying that I took one and cheated. I have never cheated on anyone before why would I start now? I tried taking to him last night but he was just ignoring me and tellling me to leave him alone, this made me angry because I know I didn’t do anything wrong so why is he even counting them? Why is he automatically assuming I took one? We’ve had this happen before where a “conform went missing” and I was automatically blamed. I don’t know what to say or do, I’ve told him repeatedly I didn’t do anything but idk if he even believes that. But it’s really upsetting and I don’t know what to do or say.