Totally agree with Bulle... try to divert your mind from thoughts of her by doing stuff you like. Maybe try doing new things too? Hiking? Road trips? Dunno, the list is endless, but the experience is gonna lift your souls up. Also, maybe try actively searching for some other girl- you shouldn't necessarily develop a serious bond with any girl so quick after a breakup- but,you know, get in company of girls, do stuff with them.
Also, wistful masturbating works wonders- especially if a tinge of a feeling of revenge is added to it.
But dude, a word of advice from my side- try not to get too emotionally attached with a girl unless you're really sure its gonna work for a proper amount of time. The moment when things would come crashing down, you're gonna have a problem. Maybe its just for me, but still.
</3
Anyway, hope it gets better for you soon. Also, TW banter works wonders, you know, chat more with people here if you'd like to.