Oh, I can relate to much of this. I have Borderline Personality Disorder, and it is a struggle not to act that way in all of my relationships.
The thing that helps me most in my relationship, which I have been in for over three years now, is remembering that my boyfriend wouldn't be with me if he didn't want to be. If he didn't think I was pretty, he wouldn't tell me that I'm pretty. If he wasn't attracted to me, he wouldn't have sex with me. And as a bigger girl, I can understand having some weight worries. But over time, I have come to absolutely adore my body! My boyfriend loves it, too, so I don't have to worry there.
What I would do if I were you is maybe look up some DBT skills. It has a focus on mindfulness and taking things as they are, not how we perceive them to be. That way, you begin to see the facts of situations, rather than your worries/insecurities. If there is, in fact, a problem, you learn to problem solve, not just react emotionally. There is also a module on interpersonal effectiveness, which would be very beneficial to you, I think. It is a long process to changing how we interact with other people, and especially how we think, but it is worth working on for both the happiness of ourselves and others. And if you're up to it, maybe try to figure out why
you are feeling this way. You are not in any way, shape, or form hopeless. There are always ways we can get better.
If you need any help, always feel free to private message me! I'd be happy to share my own personal experience or methods I have learned in therapy. Or if you just need a random person to vent at, instead of your boyfriend.