When I Was Small It Was Just "haha You're So Chubby ***!" Now It's "fatty! Fat Fish! Hahahah!"

I'm 13 going to 14, my friends are all slim or chubby, I'm the only one that's overweight (72 KG, and I'm only 4"2 tall...), and usually has my pants a bit down, and people keep telling me to pull my pants up seeing my underpants, and laughing at me, while I just put on a fake embarrassed smile and fixed it, I feel like killing myself and them over and over again. There was that other time when I was "chubby" my pants ripped, I had to borrow my friend's pants and my underwear also ripped, apparently i got fatter again. And then they saw my *cough*DownParts*Cough*, and It was embarrassing to say the least, and when I was in a Church Fair, we were playing and each of us had to go under everyone's legs like crawling under them, and my pants ripped, the man saw it and cancelled the game, until know I'm fat, and ashame of it since every day of my life I've been brutally criticized, teased, laughed at by my friends, families, siblings, adults, teachers and parents. How I wish to be thin, but I can't everytime I want to hit the gym, or do something like that, they'll tease me over and over, criticizing how it will be impossible unless i take it seriously (I did, but once they start criticizing me, I feel like I'm not ready to do it...), and the cycle goes over, and over again.... And usually no one can send me to the gym, because my friends have other friends, and barely spend time with me anymore...(I have a feeling it's because I'm fat, and don't want to be seen with me when going out....). And though there are some positive effects like...: I'm warm during fall but still freezing in winter, I'm...Soft, and apparently I get many friends for being overweight so they can sleep on me during long trips in the bus or the car or bored at school.... I still want to be slim so I can get a boyfriend though... :( But ah well.... And I think I'm the only chubby/fat person in this world to usually be brooding or feel like crying.