What do I do about thinking about girls other than my gf?
That is not good. Why are you thinking of other girls?
I'm bored with her. She is fat, boring and stupid. It's ugly but the truth.
Loving someone means that you accept all their faults, for better or for worse. If you can't see past these things, I believe it's best to part ways amicably to find someone more suitable for you.
You need to mind your own business. My girlfriend is my own business.
Yes but you are hurting your girlfriend by dating her when you are not attracted to her. You should both find people that you find attractive and that find you attractive.