trust issues, help

I have a boyfriend of a year or so, and I find myself being extremely jealous and find myself having trust issues. if he likes a girls picture or reacts to something of hers on Facebook I get upset and I go into the girls profile and compare myself to her and put myself down. My brain automatically makes me think “ Oh he must like her because he liked her picture “ but I don’t want to feel like that. I know it’s not true liking picture ≠ liking girl. Or I hate how sometimes girls are on his best friend list. But I want him to have friends you know? I don’t want to be that girlfriend who blocks off every girl. I want to be okay with him talking to other girls and I feel so toxic and I keep starting issues because of this which leads to even more issues but I don’t know how to change myself and he said he didn’t know how to help me. I just feel stuck and I truly want to change.