Beginning Actor in Last months of senior year (Please help!!)?

Hi, throughout my life I had never known what I wanted to do. I've always loved psychology though throughout my life. Getting into acting wasn't a spur of the moment thing, I spent months prior to this deciding if Acting is what I want to be and am taking an after school programs at my local theatre, reading books at my local barnes&noble, and am trying to take a class that has a audit at January 5, 2011. I've always been inspired by movies as a kid. I've always wanted to be a part of that movie, influencing the emotions and hearts of others by being on stage and performing. I don't have much experience as an actor, but that is why I really need some help getting into it. I'm trying to find out how to get into auditions so I can attain experience(i signed up for a free audition website and am trying to get a response). The major concern I have is that I'm a senior in highschool and my grades and classes are not better than average.. And the past years it was not so great. I think my GPA is around 3.2.. and my SAT score was 1690. I'm just really concerned, I don't want to be anything else but acting. I'm not looking for fame and fortune, but I am looking for this career to be able to support me and hopefully a family that I want to have in the future. I really want to be an actor, because I feel it is my calling. I've never had this feeling before. The major concern I have is I don't know if I should attend college or go to AADA or AMDA. I'm just so worried that I may fail, but I understand that I will have to go through all that to become an actor. And i'm emotionally strong and i've always been through ups and downs and made it through. However, a lot of research has told me that I should attend a college as a back-up plan... but I really want to have my full undivided attention on pursuing acting as I am behind. What should I do? And also, what universities or colleges or schools should I attend? I wish I could get into NYU Tisch, but I don't think I fit the criteria and I am afraid of the audition as I have not done one yet, but I am hoping to get prepared in the acting class I will be taking as mentioned in Jan. 5. 2011. Does anyone know what I can do? I'm lost, and the deadlines for schools are very soon. Thank you for reading this, I know it is very long.

P.S. Im sorry that this paragraph may be confusing, but I am hopefully trying to get quick answers. If I don't get much replies, I will have to write a better question.