Most Helpful Girl
Okay, a real answer from a fat woman (although, obviously not all fat women are the same).
I realize that most guys aren't interested in fat women. If I showed interest in a guy, it would be because I sensed that he was a nice person who didn't seem overly judgmental of others. There was a sense that MAYBE he wouldn't be judgmental about my weight, or in the very least, he would be kind when he rejected me. He wouldn't laugh at me or put me down for thinking I might have a chance.
Secondly, I never went for the hottest guys, or guys who seemed like they had tons of girls who were interested in them. I assumed I had no chance with those guys, but also (perhaps unfairly) that they would be full of themselves and likely jerks. Obviously if I was going to date a guy, I'd want to be attracted to him, but I think I was much more forgiving of flaws that most of my friends. The guys I went for were average, or sometimes below average, according to my friends' standards. So, while you have a nice body, perhaps your face or something else about you might not be very attractive.
Lastly, I should mention that I think I was far more likely to pursue guys than my more attractive/thinner friends. I grew up believing that there was no reason why a girl should wait for a guy to ask her out, that women were just as capable of asking guys out, and so I did so. But... most of my friends didn't---they didn't need to because they had plenty of guys asking them out. I mention this because there might be thinner girls who are attracted to you, but who don't actively pursue guys, so you might not know that they're interested.