That could definitely be depression or SAD. You say you don't label it as depression, but it may be worse than you think. When I"m depressed, I usually think I'm less depressed than I really am.

As for hostility, it's common in teens. My first depression (16-17 years old) had a lot of hostility. Now, I only have mild irritability.

I crave carbs, hide from my friends, feel like crap, sit in one place for very long periods, and sleep twice as much as normal. Also, I tend to get sick MUCH more frequently if I'm depressed. (Depression can affect your immune system)

I'd talk to a psychiatrist or general practitioner. Both can help you if you're honest with them.

Otherwise, consider making sure your living environment is well lit and warm. Try to get a bit of exercise too. I know it helps me.