Thank you for that additional info. I'm going to make a few suggestions and give you a couple of links and you can let me know if it helps.
The first thing to think of is that you are attractive....and that you are not gross. If you are unhappy with your weight, then you can try and do something about it, even if it means just walking more and making better food choices. You have had other boyfriends, and this one seems to love you very much, so that means that you are attractive to them, even if you are not feeling particularly attractive yourself.
When it comes to performance, most guys are just so happy to be having sex, they aren't using a scorecard. As you get more and more comfortable with your partner, you can try different things, he can learn what you like and you can learn what he likes and things can get better and better as you go along.
Many women cannot have an orgasm from penetration alone...they have to have clitoral stimulation, coupled with penetration, so you might want to consider starting there. Using the vibrator as your boyfriend penetrates you. I'm going to list some links below for you to go through. Don't feel freaked out, people have them all the time, they won't hurt you. Put yourself in a relaxed situation, soft music, soft lights, and it may even be better for you to try having an orgasm by yourself, so that you know what to expect and how it feels.
I welcome your thoughts, let me know if you want to talk more