I look like a freaking kangaroo?

Ugh i feel so fat all the time. Ive never ever weighed over 100-105 lbs and now i weigh 120... Its really starting to depress me as all this weight is in my belly/hips. i fell like i have a kangaroo pouch! i am only 16 and am roughly 5'2" i gained this weight so fast that my mom actually thought i ws preggo and made me take a test. talk about depressing... it doesnt help that i work at mcdonalds and with the economy as is we've been super slow and with no customers i just stand around and eat... I have no will power and dont like other people seeing me exercise. its too cold to go running. what are some exercises i could do quietly in my room? If i dont lose this weight in like a month im just not gonna eat and see how that works out.