Some people bring out our true nature, that being an uncharismatic nerd in your case. You need to realise that there is nothing wrong with being a nerd. I'll give a personal example. Awhile ago i was out with some friends that i've met through online gaming, utter nerds the lot of them. We hooked up with some girls and one asked how do we know eachother (as we were very different in age etc) one guy said "oh, we just kinda met through a hobby". Which is true, kind of. The girl asked "what hobby?" and they all went all squirmy. I just said that we're nerds and we met online while playing an MMORPG. The guys were all like "you idiot!" when in fact she was impressed by the honesty. I'm sure you've read some of my replies here, do i come off as a nerd? Well, i am and i don't hide it or try to act like i'm not.

Hope you get some ideas from my post.