Weird prob...but someone help me gain my confidence back !?

Okay well i'm 16 and i have a bf and all,hes the school's hottest guy...but well the problem is that you know people tell me gal ur too skinny before that never used to affect me because i used to think that everyone is different,they're meant to be the way they are,but well now its getting to me like i've started feeling that i'm too skinny....like my bf's cousin tells me gosh ur like a drum stick,ur friend looks better than you,that kinda pissed me off....i feel really bad now...like why am i so skinny i'm 16 and i weigh only 40 kgs and i'm 5'3...a lot of guys are attracted to me...because i'm pretty,well that's what i have i have nothing else in me plus i'm only a average student...someone just tell me what am i supposed to do,i'm totally gone psycho,like when i dumped my ex bf he said u don't even have a good body,but now its like circling around my head...and well the only thing i have is a pretty face nothing else...someone tell me what to do ! pleeezzz...