What can i eat to lose weight?

im a work out freak! but i work full time. i get up at 5am and usually get home from work at 5 pm. but then i eat dinner and have to go to school from 6-10 pm. i eat yogurt and salads pretty much everyday i dont snack. and somehow im gaining weight? how is this possible? and i only dirnk water i would rather eat calories before i drink them. i also eat lean cuisines and i have no time to work out. i try to do about 150 sit ups when i wake up but thats all.