Dating a guy does not denote exclusivity. You have to accept the fact that if you are dating someone, he may be dating other girls as well. It's just how things work until you two declare that it's a relationship. And if you think about it, that's how it should be. It takes time to realize that someone you're dating is the only person you want to be with, and vice versa. It takes time to really get to know a person, and you shouldn't let yourself fall for someone if you don't think you truly know them.
Your focus shouldn't be on finding that one special person right now, especially with your current fears. Your focus should be on getting yourself out there, having fun, getting to know people, and then when things seem really, really right with someone..then you take that plunge with them.
"If the dealer dealt a ****ed up hand of cards you gotta play em." - OutKast [Humble Mumble]