brown discharge immediately after sex

so I am on the contraceptive yaz and the day after I took the last placebo pill my fiance` and I had sex before I took the first pill in the new pack. i'm a little over half through the second week of pills and i've noticed this week that after sex I have a brown discharge. I took an at home pregnancy test, but I believe that it would be to early to get an accurate reading but after taking the test it showed up "negative" I guess i'm just wondering if i'm ovulating, since that seems to be a popular answer for the brown discharge question or if i may be pregnant.