My uterus hates me! Sorry wrong GROUP!!!! A little tmi

Corissa
Ok, so my SO and I BD 3 days before my ovulation window. (My SO had surgery the day my window started.) So 3rd day of my window I thought I had what looked like implantation bleeding, had some cramping and pain. So now today I have some brown discharge but it's not time for AF for another like 3 weeks? So I'm just so confused? Has anybody else had this ever happen?