Im gaining weight?!?

I eat really healthy most of the time and i cant stop gaining weight! i dont over eat, i dont dink pop usually, i eat regular ballanced meals, lots of fruits and veggies ..i dont know why im gaining this weight! i feel disugsting. i went from 174 and now im up to 178 and im trying to lose weight! HELP! i feel disgusting i dont even want to go outside right now. i just started doing tai kwan do and im supost to lose weight, not gain it. help! how can i get to be like one of those pretty girls? im so disgusting. i want to cry. ive gained 40 lbs in 3 years, this isnt cool! and i dont know why! i eat better now then i did in college. please help.