Blood in vagina but not period?

Sorry if this doesn't make much sense and quite Yahoo Answer - esqe but...
my period is about three days late and  about a month ago i started the pill. Earlier today I was checking to see if my period had started. I noticed a stringy brown discharge sort of stuff and was confused. It wasn't enough to be early period and it was very light and stringy. As the day continues, extremely small amounts of dark brown and occasionally bright red blood would appear on toilet paper. as gross as this sounds, I tried reaching up there to see if there was more, but there was none.
I'm very confused and sort of scared. i was sexually active before i started the pill but we used protection. any thoughts?