Babe, there's all sorts of ways to do this... I can't imagine the "I have a fetish" moment, because for me, it's always just been instinctual. I like a girl, and she likes me, I tickle her.
If this guy likes you, and if he's a decent guy who wants to give pleasure to the girl he likes, he'll probably be cool with it... But I wouldn't go for the whole explicit statement thing...
The next time you two are making out or engaged in foreplay, give him a subtle poke in the ribs. If need be do this a couple of times "by accident", until he jumps or jerks a little. Then, it's "Look who's ticklish!" You tickle him. Out of competition, an attempt to maintain some semblance of male dominance (or self-defense), he'll probably take to tickling you. If you want to be tickled more, keep goading him on until you're satisfied. Afterwards, you're presented with a great moment where you can say, "I really liked that. Would you like to tickle me some more?" Better yet, dare him. Give him the bedroom eyes, and he should get where it's going... If he doesn't want to, maybe he's not the guy for you.
Just a thought. Good luck, babe.