Could something be wrong? Need advice.

I have a very regular, 30 day cycle. My period isn't due until September 6th and yesterday I had to use a tampon for a couple of hours because I had light brown discharge for a few hours and then it went away. 2 days ago I wiped and saw maybe 1 tsp of light pink/milky discharge but it didn't happen again after that. My period wasn't due for 10 more days at the time. My Basal Temp was 98.2 all month and spiked to 99.0 starting 3 days ago (assuming that I ovulate much later in my cycle than most people). We had unprotected sex 4-5 nights a week all month long. Could the brown spotting be a short and very early period? Or could I have cysts? What could have caused it?