Trouble Approaching Women?

First of all let me just state that I am a gr.12 high school student. (Age helps individuals form answers sometimes). To get the point, I will state that I have never had any positive luck with women. I was always the nice guy who was always there for them. However, when I actually voiced my feelings toward them, I always was the recipient of one of the following. A) I am laughed at, B) I am rejected and told that "I am not good enough," or C) I have been led on. Now simply, because of these unfortunate occurrences I have not a single amount of courage in approaching women. I know many of you will probably think "You have your whole life ahead of you..." I understand that concept, it is just the fact that the loneliness kills me. I have very loving friends and family, it is just a whole different type of loneliness that I struggle with due to never having a chance at a relationship. Alas, my prom is approaching in a few short weeks and I am dateless, which given my circumstance, bothers me a considerable amount especially most of my friends have dates. There is a girl who I have been gaining interest upon, however I have never personally met her (she is in grade 10). What I ask of you fellow readers is if you can please share your thoughts and opinions in general, as well as touching on your methods of "gaining courage" if you would be so kind. All help is greatly appreciated. Thank you all in advance!