Paranoid

Alright ladies!! So on Thursday July 21, my boyfriend and I had protected and unprotected sex & I saw he didn't cum in me at all both him and I are VERY cautious about that.. my period was suppose to start Friday the day after. That Monday I took a plan b pill as well, I may sound very uneducated or not very bright but is it normal for sex to delay your period? I'm feeling cramping where I normally would when I'm about to start my period and I'm bleeding a little bit.. should I be very concerned?