Why did I suddenly lose the desire to eat?

Hello, I am a 16 year old male. I have suddenly lost the desire to eat. The thought or visual of food actually makes me nauseous. My breakfast this morning I had to wolf down, and I'm having trouble keeping it down bc the thought of it alone is disgusting. I realize I need food to eat and survive, thus I still continue to eat. I don't want to eat food because it is repulsive. The root of this issue remains to be seen. School starts in under a week, and that could contribute, but this has never happened before. I recently started talking to a guy, I don't know why that would contribute to my problem but it could I guess. I have been wanting to lose my weight for the longest time. I feel as though I am fat, but others say I am not. Sometimes I want to starve myself to lose weight but I know I shouldn't so I don't. Is my subconscious making me repulsed by food to get what I really want? Which of course, is to have a very low body fat percentage, and mostly a flat stomach? I'm not sure, I know this isn't healthy, and if I told my dad he wouldn't understand.

1. What is wrong with me; is it an eating disorder? If so, what kind?

2. How can I cure myself of this?