Why can't I stop looking? I think I'm messed up.?

Oh geez. Where to start? I have a great guy. He treats me better than anyone ever has and puts up with all of my crap, but I can't stop looking. I always think oooh, I wish I had someone taller or hotter or more sophisticated. I don't cheat or anything. I've had other relationships before, and I've been with people I found more "impressive," but it never worked out. With this guy, I am completely myself, and I'm adored. Is it normal to always be looking for something else? I feel like I do that with everything, like I'm never satisfied. I think I might need some counseling.