Pregnant?

I've been talking to this guy since October, we've been sleeping around for a while now and we haven't been using protection (that's my stupidity but besides the point). two weeks ago we slept together and he pulled out but I'm not 100% about the precum thing i guess. I'm a nervous wreck and keeping my issue to myself. so far I haven't missed my period but it's supposed to come in two days. I might be psyching myself out but I need a little reassurance. Could it just be a mental thing that I'm just over thinking or is it reasonable to be over reacting and scaring myself or should I not be living in fear. I don't know but I need advise