Scared of getting eaten out again

So an asshole ex of mine fucked me over in a lot of different areas, one being getting eaten out. After we broke up, he said some really mean things to me about it like it smelled like fish and he only did it to get in my pants and that I suffocated him with my fat ass. And He was the first guy I ever sat on his face and now I'm with my new boyfriend and he's never had a girl do it and I want to please him but I'm so nervous about it like I can't do it anymore he's gone down on me but I'm too afraid of what he'll think if I sit on his face. Help??