Please help me!

So yesterday I had sex with my gym trainer for the first time. We have talked on and off for the last year and we have always had more of a relationship then other trainers did with their clients. Yesterday it finally happened. But he is like perfect and I am definitely not there yet and I have lost a lot of weight so everything is kinda loose and I am very uncomfortable about how my body looks. I think I look good with clothes on but not without... anyway it was my first time and because I was uncomfortable I couldn’t really initiate anything or really do anything for him. Don’t get me wrong he was great and tried to make me feel better. But I just kinda need some advice on how to get over that and just enjoy it and also what to do in the moment. Because your girl really needs some help lol