How to overcome anxiety/Fear of rejection with girl I like?

I like a girl who is in two of my cles.I am the shy type.She is truly beautiful to me.I am infatuated by her personality/looks.Me and he know each other but we barely talk to each other before.My anxiety is keeping me from talking to her.I have basically wasted most of my school year not talking to her.I think she likes me by the way she looks at me all the time but she is starting to look at me less.I want to tell her how I feel but to afraid of rejection so I talk myself out of it.Time is running out and I have a month left of school.So how do I tell her how I truly feel without making myself nervous and afraid of rejection.