Please please help.

I'm 17 and I had sex with my boyfriend on Friday night. (Friday 13th) Since then my stomach has been hurting really really bad. I'm very nauseous and I keep getting bad headaches. We didn't use protection but I'm on birth control (the pill) and he pulled out before he finished. Last month I missed two pills then got back on track. And I've been taking the pill right this entire month. I can't be pregnant right? Is there any possibility I am?