I had unprotected sex and my period ended two days early??

today is the fourth day of my period but I am not getting any flow. just the smallest bit and its mainly brownish red. Yesterday, the third day of my period, my bf and I had unprotected sex but he pulled out. it was a terrible idea bc he thinks some might have gone in me. right after we had sex my period instantly got lighter and its gone today. side note on the second day of my period we had sex but it was protected. I am confused as to why my period just randomly stopped today bc i usually have five to six day long periods? am i pregnant ???