I'm in University momentarily, and near the University, there's a gym to which I go to work out occasionally. I'm a reticent, introverted, non-social type of guy and I'm not insecure about it. In fact, I'm perfectly happy as is since I have no trouble with having little to no social interaction in my life since it doesn't bug me. I'm not a jerk to anyone, especially my family, at all, but I just enjoy keeping to myself. Anyways, as I was leaving the gym today, and a girl from my class shows up and tells me that the bus is down today (bad weather in the area) and asked if she could grab a lift from me to her house. I, of course, responded yes.
On the way to her house, she began talking about something pertinent to the calculus class we're both in and asked me for my number. The next day, I got a few texts from her and decided to help her out with some calculus via the texts. 3 days later, she's sending me texts every 5-15 min and just chatting it up as though she's a friend of mine. To elaborate, these texts are often just "fun" to "flirtatious."
Essentially, I'm just really confused. Since when did being 100% business with people (although being helpful) turn into an opportunity to hit on them? Granted, she is attractive (athletic-nerdy type), I'm still not interested in a relationship, period. It seems kind of classless, and worse yet, I think if I tell her that I'm not looking for a relationship at all (I'm single atm), it'll make me look like a jerk.
advice?