I know how you feel! Look for something else you can do to keep your mind of your depression. I've taken up tennis. Is there anything you are good at or enjoy doing? Is there a reason why you try to act happy (are you afraid what people will think, etc.)? Remember that your friends are your friends because they like you. Look for a group of people that have the smae interests as you (stating the obvious), and don't try and change yourself to fit in. It will only make you feel left out.
Sic Semper Tyrannis