Ok, so I'm not a person who gets along with other people very well, and there is this one guy who happens to be my enemy, and out of all my friends, I'm the only one he hasn't dated because he doesn't like me, but I have a huge crush on him that I always hide because I don't wanna be embarrassed by his "other friends", but anyways, is it normal?

...He probably turns you on BECAUSE he's your enemy, and it's forbidden, but I dunno. I'd go with NotFloydzie. If you really like him, try and befriend him.
I had a friend who was in that position, this guy had dated all of her group of friends except her and she felt exactly that way. The guy used the situation to his advantage and ended up putting a massive strain on all of the friendship group. The relationship lasted only a couple of months in the end, and she regretted wasting her time on him afterwards.
It probably sounds like I'm scaremongering, and I probably am exaggerating a little. But consider that you might only like him because you feel lower than your friends, and as soon as you have him your attraction might disappear. In short, the sort of guy who has dated all your friends probably isn't the sort of guy it's worth going out with.