What Are The Chances Of Pregnancy After Brownish Discharge?

nHi. I am 17. about 5'6" and weight 126 Ibs. i had sex unprotected sex on the 3rd but then took plan b. then i had protected sex and the 4th i also had protected sex but i didnt take plan b or anything after. im concerned if im pregnant because on saturday the guy did come but inside the condom he said. should the plan b have been working for when i had sex saturday too? my period ended may 28th, so i think i started ovulating last weekend..im not sure. i am having brownish discharge but i think thats just from the pill, right? and it smells and when i wipe, there's some blood....should i be worried about being pregnant?