From what you have described, you have an unhealthy obsession developing with food. You are beginning to become more aware of calories and your self appearance. The fact that you are aware of this is a good sign though, because you are making conscious decisions, but if you continue to worry nd feel that you are slipping, try speaking to your doctor or a mental health specialist to discuss your problem /x/

Keep eating your breakfast lunch and dinner! You will be in BIG trouble if you don't.
You are NOT fat, you are underweight. If you reduce the calories you eat, your metabolism /will/ slow down. If you eat slightly more again after that, you will gain weight again. You are still growing so you need to eat healthy and enough. If you restrict, you might miss out on growth. If you really feel your fat, make sure you tell your parents and go to see your doctor together.
Remember: Keep eating! Don't skip meals, EAT when you're hungry, please don't starve yourself. It won't help you lose weight, it will help you lose healthy muscle and gain fat afterwards. That's not something you want/
I've been there, still there and I wish I never started counting calories in the first place.