Possibility of Pregnancy, or Something Worse?

OK, I need to figure out if I am pregnant or if there may be something much worse happening to me.

My son Creid was born 14 months ago, a preemie, and I had A LOT of problems with my own body after he was born. I had pulmonary embulis and gall stones. Due to lack of medical insurance I could not have the surgery to have my gall bladder removed. I had, however, a great doctor prescribe me pills that would make it easier to pass them as well as make them smaller.

Onto the problem. My boyfriend and I have been having intercourse extremely often (3-4x a day). My last period ended April 4, 2007. My periods are normally regular. It seems as though my period attempted to start this morning, but gave up this afternoon. I have been feeling dizzy, nauseus, and headachey for the last 3 days. I've also had an increased appetite and horribly bad cramps for over a week.

If anyone knows what's going on, please help. I need to know if I'm pregnant or if I may need immediate medical attention. Thank you.