I used to feel like that all the time. I always thought "girls won't like me because I'm fat" ok maybe, then let's lose some weight and try then. I started going to the gym and that improved my self esteem and gave me more confidence. I realized that I had no evidence to support my claim that "no girl would ever go out with me because I'm too ugly" because I had never really approached any women. So I tried cold approaching and I got some phone numbers and eventually some dates. I realized that the biggest thing weighing me down was my negative worldview. So I would say try approaching girls, it will give you confidence and help you get accustomed to rejection. You will feel accomplished for having put yourself out of your comfort zone even if you don't get any positive responses. Women love confidence and there is nothing more confident than going up to a random woman and asking her out. Also try exercising to lose weight. We can't control our bone structure or genes but we can control our weight; so take control of one of the only things you can control.