Is fresh vegetables and fruit really that expensive?
Just asking, I'm from South Europe, its always something awesomely delicious in season and cheaper than imported things. The prices here don't strike me as more expensive than pasta, meat or even fast food. But I agree that 20$ isn't alot though.. For any kind of food.. Can you share your expenses with someone, roomate or something? It's always cheaper to buy groceries for more people..
Like someone else said don't go super strict on yourself! Drink only water or tea, try to fill up with nutritionaly dense food like green leafy vegetables with every meal so you feel satisfied, if you like meat and fish go for the lean cuts, if you like carbs - eat them, but go for complex carbs.. I am not a believer in low-carb diets.. But the important thing is to eat something healthy that you LIKE. Don't torture yourself! And don't think about what you can't eat.
And exercise every day if you can! Can you ride your bike to work? Do you have a treadmill or something? What do you like? Can you find an exercise buddy?
I'm running right now. I hate it but it really helps, so while I run I think about how great I'm gonna look if I keep it up

And I finish every time.
You can do this!