Embarrassing question...?

Ok, so about a week ago, I started having a really dark brown discharge, well i dont even think it's discharge. It's like the really thick string of goo. I either have that or really light blood. But no matter what, when I wipe the toilet paper is dark brown. I haven't had sex for nearly two months now, so I don't think it's an STD, I'm thinking it might be because I forgot my birthcontrol pills for three days, and I mentionned that to my best friends mom and she MADE me take all three of them at once, ontop of the one I had to take that day... could that be it? Or should I have to go see my doctor?