Spotting brown for 3 days... anyone have this problem?

I am TTC #2. I have been having irregular cycles. They usually are 25 days but it varies 22-26. Used a OPK and it said i was due for ovulation. We had sex before that and on the day of. 9 days after ovulation i had brown spotting but it was only there when monitoring my cervix it was super light and barley there. (Brown mucous) not even "blood