it sounds like you are depressed with the negative thoughts and no emotions.
usually teens are hit with this horrible disease depression. i've battled this monster for 1/2 my life.
you should talk to your doctor and tell them how you feel, and how long you've been feeling this way.
why would you hide the fact that your depressed? it would be nice to know that they would be more understanding to you, your parents was teenagers i m sure they went through the same thing.
are you able to talk to a school counselor also?