What's up with my appetite?

I'm a 16 year old girl and I have had a HUGE appetite lately. I've always been pretty slim and never really had to worry about my weight very much. I am 5' 5"ish and normally I weigh somewhere between 112 and 115. It fluxes. I've been more aware of weight and nutrition since Christmas break when my sister, my cousin, and I had a weight loss competition to see who could loose the most by Christmas. I ate really healthy for three weeks and went from 115 to 110. Ever since then I have been very aware of my weight. I am always worrying about eating too much and counting my calories. Within the past 3-4 weeks I have been eating SO much. Even if I'm not hungry I want to eat. I have been stressed lately because I had AP Exams and lots of homework. My mom says that I'm just stressed, but I'm not sure that it's that because I finished my exams today and my appetite is still the same. My aunt told me that it's just a growth spurt, but I don't have any growing pains. I just feel so guilty after I eat and then I just don't stop eating. I just wanna eat constantly. What is wrong with me? Am I going through a growth spurt, is it stress, or am I loosing control? Can you give me some tips on what I can do to stay slim but be heathy? What can I do to limit my crazy appetite? Please give specific advise. Thanks so much!