I'm still not sure about this girl?

Even though I give great dating advice, my advice means nothing when it somes to me. I really like this girl, and she's shown all the signs that she likes me, but I'm still unsure. I just can't see why she'd like me bacause Im a jackass(the good kind=D) and she's an amazing person. Every time I get to talk to her alone my friends come ove and start talking to me, then I get so pissed. I want to ask her for her number but every time I have the chance my stomache drops. I know she would give me her number because she went to one of my friends to try to get my number ( which failed because he's a dumbass) but I'm still just too damn nervous. Every time I look at her I get all angry inside because I'm mad at myself for not talking to her. Can someone please give me decent advice?