What are some things i could do if in stressed out and every little things annoying me?

I'm in highschool and lately i've been really stressed out because of school, and life in general.. my three brothers keep annoying me and i feel bad, but i can not help but to yell at them.. it's like everything they say or do is ten times worse in my head and i just get really angery.. also, im a thin girl with a fast matbilizm (if thats how you spell it), so i can pretty much eat whatever i want, but lately ive been eatting ALOT and not healthy but all junk food. i stayed home sick the other day and found myself going to the fridge every 20 minutes. anyways, i know i need help but what can i do? thanks(: