Because sadly being your age is supposed to be fun, but it's not. It sucks, you just have to wait it out and not get down on yourself. Don't worry about being popular either, it's pointless.
Because you allow others to see that you care to much. Either stop caring or find a way not to show it.
bth People can feel desperation. It pushes them away.
Because your young.... the path you choose can be difficult ... the life you lead is your destiny...
You haven't had the chance to realize how amazing you are. Just wait until you find your niche in the world :). Try working hard at trusting yourself and believing in yourself, no matter what others say. In high school the insecure kids are more likely to get picked on, it doesn't say anything about who you are.