Ummmmmm.... I dont think the "not living with my gf" solution isn't the best idea. It'a really hard to take a big step back like that. But then again, what do I know.
What exactly is the living situation? House? Apartment? Whose name is attached to whatever. I think if you've been with someone for a while, and then find yourself dis-interested, it's time to cut bait. Dont waste eachother's time.
Let me give one disclaimer though, I always suggest you let the other person know your feelings first and give them time to improve the relationship if they want to. That's my biggest complaint when recently getting dumped....I had no idea there was a problem and was never given a chance to show her I could make things better.
"Oh Lord it's hard to be humble, when you're perfect in every way. I can't wait to look in the mirror, cause I get better loking each day. To know me is to love me, I must be a hell of a man. Oh Lord it's hard to be humble, but I'm doing the best that I can." Mac Davis