I have PCOS (Polycystic Ovary Syndrome) and I have severe pain on my left side every other month. I thought it was always just regular ovulation until I had an ultrasound done on my ovaries and discovered I have cysts. If you're very concerned, or feel you may be pregnant, I'd call your doctor right away. It could possibly be an etopic pregnancy, or it could be nothing. If it continues next month, or the following (if you indeed ovulate alternating sides each month) I would have your ovaries checked. You could have a cyst that might rupture. Good luck!