Guys tend to be very visual when it comes to who they are attracted to. Young guys tend to be attracted to lots of girls at the same time and don’t have the same kind of “lovey-dovey” feelings that most young women have, it’s mostly about lust. So for guys it’s easy for them to move from one girl to the other without even thinking about it.
He probably liked you for a little while and then when this other girl came along (or became available) he probably decided that he liked her even more. It doesn’t even matter whether you think she’s a bitch or not, because he doesn’t think she’s a bitch. She may have thrown herself at him and if she’s all dolled up with makeup, he may have really enjoyed the fact that she kind of looks like a hooker. Like I said, most young guys are all about lust, not romance or commitment or even friendship.
But there are guys who do enjoy romance and friendship, but you have to be willing to date guys that don’t fit your usual type. Some times the nerdier guys, the one’s that are not the cutest guys at school, or the ones that aren’t the best at sports, turn out to be really great, and later in life, they really bloom, where as the guy in your situation is not likely to get any better than he already is and in fact, he might even get worse.
I’m sorry that you got your feelings hurt by this guy, but just try to move on, and don’t bother blaming the girl, it will just make you look petty. And don’t try to get this guy to explain to you why he stopped talking to you. If you do, he’ll probably get really mad and might likely talk about you behind your back, just to make you look foolish (instead of him). So just let it go and try to find some other more worthy guys : )
And learn now, while you are young, to take the high road. If any of your friends or other people pester you about why this guy is now going out with the other girl, don’t ever say that she is a bitch (even if she is) just say that he must really like her, and leave it at that. It will make you look like a much better person