What's the fastest way to lose weight for my lifestyle?

I want to lose at least 20 lbs. by the time June comes. The problem is that when I eat, I am extremely picky, and I live at my college, so the the food they provide are not that healthy. The fruits I like are only apples and gs, and I don't like granola bars nor oatmeal. I do exercise 3-4 days a week and I am stuck at a plateau. I'm just so confused on how come I don't lose weight. Thanks for the advice!