I got my last period on Sep 2 and had sex one Sep 3rd, still on my period. It was unprotected but my boyfriend did not completely finish inside me. Recently i've been exercising more and i heard that it could be a factor in changing my menstrual cycle. On Sept 23 i experienced some bleeding, and it was extremely heavy like my normal period, now today it's almost completely gone. Could that have been implantation bleeding or just my period coming early. i've been really stressed because i was NOT planning on getting pregnant and am only 17. please help