Feel fat help plz :{?

so i get called names wide fat hippo flabby im 12 and im 112 im 5,8 im more a pc geek then a athlete but i get made fun of and now my mom says she gonna get gym member ship and get me a trainer i cry alot and try not to eat but i get hungry school i give most my lunch away but i keep getting hungry i don't wanna b fat i hate my body now i use to b ok but every says im fat