I need serious advice. I'm in a relationship with an objectively STUNNINGLY beautiful girl -- seriously a 10. We met in high school, dated, broke up, dated again--total, about 6 years together. Just recently got back together several months ago, and generally things are going well. While we were off I slept with two other women--she's only been with me. She's super smart, graduated from an ivy league college, and very successful. 100% marriage materail. Also for some reason loves the heck out of me.

Here's the problem--I'm 26 years old and I don't find myself that attracted to her sexually. She's got a rocking body, and SHE has a higher sex drive than I do most times. But I don't know what it is that makes me unattracted--maybe it's because there's just 0 challenge anymore and I can have her whenever I want. I find myself (very often) looking at and thinking about other women. There are times during the day when I feel so fantastic about our relationship and other times when I feel crappy--it's a freaking roller coaster and I don't know what to do about it. I'm so far in my own head it's crazy--part of me wishes that she would have slept with someone else at least when we were apart, but for some reason the fact that she's only slept with me ever bugs me I think, although I can't exactly pin down why. I want to get out of my own head and be happy with this girl. I love her--and I understand that the "mystery" of a new relationship or sexual encounter is something that I can't really have again, and that's fine. Help please!