You won’t like what I’m going to say but it must be said: You are in no way ready to move in with your boyfriend. I think your obsession with his past is how you are telling yourself exactly that.
You say that you are quiet, that you don’t like to party and that you are just about to start college. You’ve been with your guy for less than a year. My best guess is that you are clinging to this relationship because you are nervous about launching a new life at school.
Furthermore, you are not as mature as you think you are. You worry about whether you are pretty enough and you have gone searching for pictures of your boyfriend’s exes. Those behaviors do not indicate maturity and positive self-esteem.
College means new friends, new experiences, experimentation with new ideas and a developing sense of self. It is a difficult but very important transition for many young people. But it is an important time of self-discovery. All that will be minimized or even eliminated if you are trying to make a home and a life with your boyfriend.
Being 7 years your senior, your boyfriend has already gone through that developmental transition. He knows who he is and what he wants. From what you told us, I don’t think he’s a “player”. I think he reacted in an immature way to his cheating girlfriend when he was young. If he has matured, he will understand that you need time to do the same personal work that he did.
My advice to you is that you and your boyfriend take a big step back. By all means, enjoy each other’s company. But don’t be exclusive for at least a year. A 7 year age difference isn’t necessarily a big one, but this happens to be an important 7 years. You need to have the freedom to explore yourself and relationships before you commit to a lifetime with your current boyfriend.
I wish you well.