<human>: Can you give me the gist of the text in a nutshell?

So basically, I just started a relationship with the girl of my dreams, but there is something that makes me so terrified than ever. I haven't been in a relationship for about 5 years and jumping on the train with someone I deeply care for makes me a nervous wreck. I have never been in a relationship for more than about three weeks with out some kind of wrongful outcome. The past girlfriends I had have all cheated on me. I have no doubt in my mind my current girlfriend right now will do that to me, and I'm not at all worried about that. What is making me nervous is her leaving me for something I couldn't do, or something I did wrong. I hope this makes sense, but I need all the help I can get. I know confidence is everything, but I need something that can make me hold on to her for as long as I can.
<bot>: I feel nervous that my girlfriend will leave me because something I couldn't do, and that she is the only person that has ever made me happy.