You know I did an entire radio show a couple of years ago on foot fetishes. Some experts say that most heterosexual men have a fetish for at least one part of a woman's body. The most common fetishes are breasts, thighs or the buttocks. Some believe that men focus on only one part because it is hard for them to take in all parts at the same time.
Learning theorists believe that a fetish develops through association. If for example, a boy masturbates in the bathroom, and happens to glance at his mother's nylon stockings drying on the towel bar, his mind can easily associate nylons with sexual arousal. It is believed that this is how fetishes develop. So, who knows, maybe you were masturbating as a kid, and glanced down at a pair of tooties at the same time, and voila, true love.
I wouldn't be concerned about your love of feet. Wanting a woman to rub her feet on your penis is also fine. The only time you would need to be concerned is if you cannot get aroused unless you include feet in your foreplay. Otherwise you are fine. Enjoy.