The fact that you are afraid you are going to lose your girlfriend sounds like a watershed to me. The rest of your post makes it sound like you've been living a lonely life but not too uncomfortable with it. Maybe you're having a personal breakthrough of sorts, fueled by the knowledge that you do care for and want to be attached to someone.
I agree that now is a good time to start therapy. Maybe talking about this relationship issue will help you become comfortable enough to deal with the others you have delineated.