Don't worry! I'm 5'8, 160 of muscle, trust me when I say you aren't big! Now in regards to your diet, your hormones are going through a ton of changes, and that effects your body. I didn't eat a lot either when I was in your position. First and foremost you need to talk with your pediatrician and parents (I know it might seem awkward but honestly they have real solutions that are best fit for you). Stress can also affect your food intake, and so can food allergies like gluten or dairy intolerance, some of which don't show up until later years!
Secondly, big changes need to happen with your diet. Not only should you change what your eating, but the amount and when. The largest meal of the day should be breakfast, but if your like me and used to get sick when eating a lot in the morning, you need to experiment with what your stomach prefers. Things to think about are items that are high protein and good fats, to keep your body sustained, and energy for your brain (which is a much bigger deal than many realize, especially as a young kid when you burn through energy like no tomorrow).
In regards to you not being able to eat at correct times, your body could be off kilter. Like a train, your body runs best on a schedule, so it might take some time to get back into eating at the "correct" times. I would suggest several small meals throughout the day instead of three large ones, it keeps your metabolism high.
Check out my earlier posts on great, healthy, nutritious foods that taste amazing, and will keep you going!
Hope that helps!
yah but I like can't get myself to eat when I'm supposed to
You should not be worried at all.
However, it may be beneficial to change your diet. It is important to eat at least three meals a day instead of a snack and then a large one at night. It is healthier.
Well the breakfast and lunch you should eat more and limit dinner to 1 serving. I am not sure of anything is wrong but see a Dr and you can talk with him/her about a better controlled eating habits which will allow you to eat more balanced meals.