Bleeding during sex?

Ok, so I'm on cd32, pretty sure I'm not pregnant, and am taking progesterone like my Dr said to do post-ovulation. Well tonight hubby and I were having sex when we realized I had bright red blood coming out of me. It's not a period, it's stopped now, and this samr thing happened a week ago too. I have no pain during sex at all, does anyone have any idea what could be causing this? Does prometrium cause it? Or can femara? I took that on cd3-7... I'm calling my Dr on Monday morning but trying not freak out in the mean time!