Well first a lot of girls cry over guys. I have done it. I am not saying we mope and drag ourselves around but it happens. You are crying over this guy because you have feelings and a heart it is natural. Doing this doesn't make you a weak person. Plus around your age hormones come into play and they just basically suck. It is normal.
Now for you to stop crying this could take time or you could just make yourself strong and challenge yourself not to cry. Just try it. You know what I am saying? (trying not to confuse you) When you feel yourself becoming vulnerable distract yourself right away or tell yourself that "i am not gonna cry" This could be difficult but I know you can do it. There is nothing wrong with you because you are crying over this guy. GOOD LUCK. YOU CAN DO IT