He loves you? And he treats you like dirt?
C'mon sweetie, take a step back and re-read what you wrote. The way you describe it, this guy has hurt you, used you, cheated on you, dumped you for his ex, and refused to talk it out. If somebody treated one of your friends like that, you'd probably (hopefully!) tell her to drop him like a hot rock and find somebody worth her time and energy.
You are a worthwhile person. You know how to treat somebody well in a relationship. I also suspect that you are plenty attractive--weight isn't everything, as you will find if you explore this site a bit. Have confidence in yourself. Enjoy yourself, enjoy your friends and family, and enjoy life. Sooner or later somebody will come along who values you as you deserve and is worth your time. The guy who dumped you is the loser, not you, and maybe one of these days he'll realize what he gave up.
In the meantime, I know it can be hard being a single in a world that sometimes seems to value being part of a "couple" more than anything. But the truth is, you don't need a romantic partner to make you a worthwhile person. You are a great person all on your own.
And finally, the next time your little brother asks you a personal question for which you aren't sure of the answer (or maybe even one you do know the answer to!) tell him it's none of his business!
Take care of yourself.