This is how I am as well. I am not sure when it began for me, but theres something that stands out in my mind. I was 13 , at my Christian camp, and was just completely obsessed with my camp counselor. I would get excited to be around her or talk to her and make up things so that she'd have to take me to the side and talk. She would dominate my thoughts later when I went home and later when I returned to camp, I made sure to make the request to have her as a counselor again.
I've read that this attraction to older women can be a result of an older woman accidentally stimulating you at a younger age. I definitely had those "warm" feelings when talking to her but as a result of my very sheltered upbringing, I still had no idea about sex.
Anyway, that was a long story. I still have a HUGE thing for older women. Men just cannot compare. Girls my age can't live up. Women are the only way to go for me these days.