4 days late.

I'm four days late for af and I've taken a pregnancy test and it was negative today. I'm nauseous, my acne is terrible (which I never get), and I'm having severe abdominal cramps for about a week and a half. so bad that I've bought about going to the hospital cause they hurt so bad. Usually I just have mild cramping. Anyone know what could be going on with me? I had small cysts as a teenager but nothing that they had to monitor or anything. I just don't know what's going on.