Horrible Irritation!!

Ok, so my boyfriend of almost 2 months and I have been having sex pretty regularly. He's my third partner and hopefully my last, but I'm 18 so you know how that goes. I shaved last night & didn't get all of the hairs. Now there is some serious itching and irritation down there & it won't stop. I don't know if it's from shaving or having sex right after shaving or both. But this pain is unbearable, what can I do to stop it????