My favourite aspects of your excerpt are "damper" and how you make a big deal of her talking to another guy, and my favourite favorite favorie: I suffer from nervousness. It makes me chuckle. Nervousness is not often a disease, especially in HS and in situations like these...it is normal, and everyone gets nervous at some point. Also It looks like you are either a freshmen or sophomore according to your age. If this is the case, #1: of course high school girls and boys are going to talk to eachother, it is not automatically going to turn into something more. #2: Just ask her out. If you really liked her, nothing would come in the way, not even your chronic nervousness. The most she can do is say no, but at least she will keep you in mind, if there is even a slight interest.
Your welcome man of mystery