Thanks for the replies, even what's been said so far is helpful.

I think it's just a sexual thing... we definitely have a lot in common (same field) and she really is my best friend-- I look forward to sharing things with her, hearing about her day, etc. I just wish there was more sexual attraction there.

I know honesty is the best policy, but I don't imagine saying "hey babe, I find myself sometimes not very sexually attracted to you. I think a lot about other women, and I wish you would back off more/not give yourself to me so easily so that I feel like I need to work for you (or something)" would go over to well. I don't think this is break up worthy, but I'm a 26 years old and I don't feel like I should be feeling this complacent in my sex life at this young age. What can I do??