Well it sounds like you were just to nice man. If you were talking about sex, then why didnt you follow up the conversation with something like
'Speaking of things that are hot and keep me up at night, you don't like coffee do you?"
or anything that demonstrates your not a pussy
. Now I don't think you are but look at it from her perspective. "That cute guy in class talked to me again today. We talked about sex, I made eye contact, there was some playful touching, why won't he ask me out?"
I say that the next opportunity you get ask her to do something outside of class. She's either gunna say yes or shes gunna say no and neither is a bad option. If she says no, then now you know that you built to much comfort and not enough attraction, and you should take that as a learning lesson for future targets. If she says yes, then you were doing everything right and just need to learn to pull the trigger faster. I'm curious to see how this plays out, let me know if she agrees to a date and then lets work from there.