I'm not pregnant, not have i ever been, i haven't had my period in about 4 months and my nipples are really sore....should i be worried?

Some: If having sex with a male partner at all, then should check a home pregnancy test to confirm if are/aren't pregnant. If not, then while not impossible to be normal for teenager, should get your gyn to check you over to be sure all ok. Can be from extreme dieting / weight loss / infection / stress, but also hormone imbalance and other problems your gyn can check you for.