Advice Please

My boyfriend and I often have sex while I am on my period, with no protection, and he finishes inside me. Then, a few days after my day of ovulation (probably 2-3 days after) we had unprotected sex again and he finished inside me. I have had sore breasts, unbelievable headaches, cramping, and nausea for about a week now. I was supposed to start my period today and have not yet, I have taken two pregnancy tests and both have of them have come out negative. Any advice of what could be going on with my body? Thank you!