100% wrong here buddy. You didn't become unattractive, you BOTH just became different people who wanted different things. That's normal, people change over time, I bet you're not the same person you are today as when you were 20. To go back to my own experience, I remember crying myself to sleep in my kitchen one night after I'd broken up with my Ex, and I remember thinking just how I should've gone out with her and her friends more rather than spend time chatting to friends on the internet and faffing around with cars. I was utterly despondent.
Today, I'm with someone who enjoys my company but understands I have other interests: Some she shares, like cars; some she doesn't, like chatting with strangers on the internet! What I'm getting at is that the person I wanted to spend my life with wasn't the person I thought it was, and I DID find someone who accepted me and tells me to go do my own things every now and then as otherwise I irritate her, but in a joking way.
Then say it. Write it all down in a letter, and send it to her. I did this, and it does make you feel better when you've said your piece.