Pregnant?!

I've recently been sexually active again, after 2 months of not having sex at all. Almost every week since March I've been having mostly protected sex. each time we had unprotected, it was only for a couple minutes. I am worried that I am pregnant now though, I'm 17 years old. This monday I woke up, went to school and felt very ill and threw up. I went home and threw up several other times, not knowing the cause. I was also supposed to get my period 4 days ago, but instead I've been noticing dark brown/red discharge coming off of the toilet paper after I pee. Please help!