I started my last period somewhere between the 16th and 19th of November (can't recall exactly). My periods are often irregular, but the last few months have occurred around the same time. I'm thinking my next one is due, at the earliest, tomorrow, but I've had severe cramping for four days now, along with nausea, headaches, dizziness, and heartburn. I rarely get any cramping at all with my period, and all the other symptoms are unusual for me. I'm not on any birth control, and had unprotected sex somewhere between Nov. 19th and 23rd. A pregnancy test came back negative, and I have an appointment tomorrow. It sounds a bit to me like secondary dysmenorrhea, any thoughts?