Girl, you gotta start lifting some weights.. makes you burn more calories 24/7 and won't make you bigger
Also be careful of endless cardio and doing things Biggest loser style, its edited fantasy and they don't show you the loose skin or rebounds, do lots of cardio because you love it, otherwise interval training is so so good for weight loss.
I told my gym instructor that I was getting into running and she was a bit like pfft I suppose its alright for stamina.
Also see on youtube BBC's Horizons The Truth about Exercise.