Had Unprotected Sex

I need advice/help. My boyfriend and I had unprotected sex for the first time and I'm somewhat freaking out. We're both pretty sure that he didn't ejaculate inside of me but is there a strong possibility that I could get pregnant from that? If so, how much is it and how long for an abortion? I'm probably just over thinking it but I cannot get pregnant and I should have known that before we did it but we both didn't plan it, it just sort of happened. Please if anyone can help me out i would be really thankful.