How do I shake the horrible feeling of depression and loneliness?

Usually around people I am mister happy, but I feel as if being such a character, I have built another personality that I do not want. Over time I get this reputation as being the one to react, people want to see me get angry or to make fun of someone else. I'm tired of wearing a mask that doesn't shows what a mature, intellectual, and serious person that I am. Now as a result to me being a person I do not want to be, I have become depressed. Now I like having friends and being very social, but thats only because I'm the person I dont want to be. I want to grow up and have a fun time while hanging out with my friends. I hope someone can help me change my persona and be the person that I want to be without losing the friends that feed off of my immaturity. Maybe you can help me get out of the ditch that I am in