Sick of this

So me and my bf have known each other since I was 14 and he was 15. I’m 23 and he is 24 we a have a 1 year old together, we have been through a lot but lately he is starting to be too much for me I’m always getting accused of stuff i didn’t he asked me to block my ex I blocked him with no problems. Now he claims that I had a secret conversation with someone who don’t know. Every time I go on my messenger and look it’s not appearing on my phone. But I made a screen recording and sent it to him. He sent me a screenshot that’s not on my phone but he claims it’s in my messenger. What should I do? Is it possible that he did something? Cause ion see it and ion know the person.