Why don't I have many friends? I think that maybe I take life a little too seriously and/or come off as being "too nice" so people think I am boring. Maybe I come off as stand-offish? Any advice? I'm pretty sure its me that is the problem.

Make sure that you put yourself around people who love you for you. A friend should have your best interest at heart. A friend will be there to support you through good times as well as bad. Work on you and who you want to be and the friendships will come