I know EXACTLY how you feel. I'm about your age, and it's funny how our problems are so similar. My parents didn't believe me when I attempted to tell them that I was depressed. I couldn't even face my dad, I went to my mom instead, but I guess in your case, it's vice versa. That uneasiness in your stomach, does it fell like you have butterflies, as if you were about to present infront of the whole school? and as if it comes out of nowhere, for no reason? well I've found something that works really well against that. just go outside, and breathe. Just take it easy and don't try to do everything at once, other wise it might make it worse. (well, in my case, it did)
But really, talk to someone you truely TRUST. Because when you do, you'll feel so much better. It may fell like no one is there, or that no one cares, but there is always that one person who does. That might sound kinda corny, but it's true.
best of luck,
p.s. post often