Why dosent anyone ever want to be with me?

I really dont understade why no one likes for who i am and not for wat i look like. When i was a freshmen(9th grade) i really liked this girl who was a junior and she did to we talk and and hung out after skool. I waz surprised because she look really nice and i didnt i was fat and she was skinny and beutiful. So i asked her out and she said yes Then my vacarions come and i surprise her by loosing weight and getting a nice toned body. We meet up and had sex. Moths go by and i start talking to more girl. All the girls loved me they wanted to go out with me and ect but i didnt but my ex thought other wise and she thought that i was been unfaithful so she cheats on me and i find out i go insane beat up the guy break up with her. I get sad and depressed gain weight. 4 months go by and i get a call from my ex she want to meet up. Wen we do she sees me an turns around and leave as soon as she saw me. Then the girls i talk to ignored me and deleted my number. My real friends dont talk to me because i didnt hang out with them because of the girls and now the im back to being the real me i have no one and im left alone with no one i try to talk to my friends but non of them even look at me i feel horrible the i have no one and it happend because i changed my self to someone i wasent