Am I depressed or not?

Okay so I'm not sure if this is depression or just teen crap. I'm 15, I have anxiety over everything, I am always down, I always just fake happy around others, my stomach is always upset, I have pains in my rib cage that the doctor says is nothing, I always overly think about every small mistake I've made, I can't fall asleep, I hate leaving my house and want to stay in all the time but I feel like a loser if I do, I don't like doing anything, and I pace constantly. I've felt like this for a couple years, but it is becoming more and more constant. I just want to be left alone. I can't even remember the last time I was really happy. Is this what most teens do, because most of my friends love going out and are generally happy. So depression or not?