Hard to say seeing as i don't ovulate on my own even though my period is regular every month.I have to be on medications for me to ovulate.But if i ovulated this month have no idea when.
I had that happen in two of the cycles I was on femara/menopur (only before ovulation, though). My RE said not to worry about it if it's only after sex. But who knows...maybe you're pregnant! The cervix is a lot more sensitive during pregnancy, which can often lead to spotting after sex. Do you know when you ovulated this month?