Not aroused by sex

I'm 26 and a virgin and just had my first sexual experiences with a girl I've had a crush on for a few months and who is also my best friend. We've really got to know each other and I feel like I'm falling in love with her. She's the most beautiful girl I know and she turns me on most of the time...
Yet...
When we're naked and kissing and touching each other I don't find it arousing at all.
I feel a wonderful close connection but I lose any desire for sex, especially when she touches my penis. The first time I was really anxious and put it down to that, but the second time I felt totally at ease with her but just lost all desire.

I'm Is there any normalness in this?