I'm 39, 140 lbs. unprotected sex with husband during ovulation time. Began mild dull cramping in pelvic area 18 days after last period began with headaches, minimal appetite, low back ache & (nauseous 1 day). 2 days before expected period, I began a light "period" lasting start to finish 2 days. Few days later comes brown spotting, couple days later I had clear mucous slightly pink. What could be going on?