Could I be pregnant??

I have been on the same pill for 2 years: sprintec. I have taken it perfectly every morning because I have my alarm set to take it. I have never missed a pill and havent had any instances that I thought could lead to failure of the pill (I havent thrown up, no antibiotics, etc). I had my last period ended on the 29th of june (I always start my new pack the Friday of my period and it ends that saturday). My fiance and I had sex over the week of the 4th of july. Out of nowhere, on the 12th of july, when i wiped from using the bathroom, i had brown discharge on my tissue. I didnt think anything of it because I have had it happen lightly after other periods as well. What scared me into thinking I may be pregnant is that when I woke up on the 13th, I had a brown stain in my underwear from the discharge. I continued to have this discharge until later that night and I havent had it sense. This increase to where it stained my underwear made me think it could have possibly been implantation bleeding? My period is not due until next Monday, so I'll find out soon obviously. But Do yall think i could be pregnant? Do you think the brown discharge could be a sign of implantation? Or maybe just my body riding of old blood before my period this coming Monday? Help!!