Brown spotting?

I am 11dpo approx. and had dark brown spotting for a few hours (10dpo) yesterday. Nothing went on panty liner, just when I wiped. Cervix is cramping or anything.  BD day before +OPK, next day I got +OPK, didn't BD on that day but tested next day and got another +OPK and BD that day. Any ideas? TTC #2 for 6 months.