Scared to have sex

I’m scared to have sex with my partner but also because of this I’m scared that I won’t make him happy.

I know a relationship isn’t about sex either it’s just I would like to not have these problems anymore or not feel like I’m the only one who has experience this before. I honestly don’t know what to do

Whenever me and my partner get the littlest bit intimate I get really scared and start stressing out about everything, that he’ll ask me to go on top and that I’m too fat and I’ll squish him, I guess everyone some what has these feelings but it actually makes me want to cry, I’m scared I won’t be good enough for him or that I won’t know how to do it... I’ve watched videos and everything to help that but when it actually comes to it I end up stressing so much about it. I really don’t know how to explain how I feel and I don’t want to tell him either because I don’t want to feel this way anymore, I guess it’s because I believe I’ll never be good enough and that I have no self confidence whatsoever. He reminds me all the time that he thinks I’m beautiful and that I could have no hair and wear a sack and I’d still look beautiful. But my past relationships have broken me and I don’t know how to fix it. I want to have sex with him but I physically can’t no matter how much I try and push myself out of my comfort zone 😔