I need a little help.

Ok so for a while now I've had a crush on this girl. I've decided that when I see her in about two weeks that I'm going to tell her how I feel. I just don't know if it's the right thing to do. I don't know if she likes me. I don't know how she will react. I don't even know how I'm going to do it so I might even mess it up. I'm already nervous about it. Should I still tell her I like her?