This is hard

This is super uncomfortable and embarrassing for me to even post. I’ve been on and off with this man for 4 years. He is only my second sexual partner and when it comes to these things I can be kinda shy. I feel uncomfortable when it comes to performing oral sex. I’m not selfish but I really just am not experienced. He always made me feel bad about my lack of attempts and about two years ago he cheated on me with a random girl and he said it’s justified because I wouldn’t do it. So of course after that I felt even more uncomfortable and really haven’t tried because the thought of being compared to other women hurts me and makes me feel like a total idiot. So here we are now. Fighting about it once again and he is calling me selfish and basically saying I don’t satisfy him. I love him I don’t know what to do. I know I sound stupid. Please don’t judge me as I am already humiliated ):