I Have Had Unprotected Sex A Lot More Than Normal

I have had unprotected sex a lot more than normal this last week with my boyfriend. My period wasn't supposed to come until July 20 but it came we early 1 day ago actually. July 10 I took a plan b pill for the first time on July 5 but I'm having a really ugly brown discharge & funky smell. Could I be pregnant? The first day my period came Tue morning it was real heavy which isn't normal for me but by Tue evening it was mostly just the discharge. So I'm just a little worried because my body has never reacted like this before , should I be concerned?