<human>: Could you distill the essence of the text into 1-3 sentences?

I'm going to college after a few years off and I've made friends. One of them, "R", is a 28 year old fitness buff who sits next to me in every class we have. We've become pretty good friends, we don't spend a lot of time together, but we grab coffee from time to time. We talk, we hang out, we study together. All of this is fine, I have had female friends before and not developed crushes.

Here is the problem...

I've seen her in spandex and it looks better on her than anyone else I've ever seen wear it. I want to see her naked, I want to shower with her. I want to take off her clothes and have "last day on Earth before the asteroid hits" sex with her... maybe a couple of times. I want to stay up all night having sex with her. I don't want a relationship with her (even though she is a great person) I just want to have sex with her and then we can go back to friends. 

A group of us were at the bar a week ago and she kept touching my elbow or our knees would touch for a few minutes, it made my heart pound! 

I'm pretty good at self control, AND I'm pretty sure she doesn't want to do the same things to me that I want to do to her. This means I'm not really worried about doing something physical to end my marriage; which is good because I am happily married and don't want to mess my marriage up. But I feel like an ass for having these feelings. It isn't fair to my wife, it isn't fair to "R" and frankly I don't really want to feel this way about her.
<bot>: I'm having strong erotic thoughts about someone I know and I don't really want to be having these feelings about them because I don't want to act on them.