I started my period at 15 and it was always sporadic, skipping one or two months at a time, sometimes coming every month for a few months. Since I started a steady sex life, at 20, about two years ago it has been coming pretty much every month. I missed last month and am now late for this month. I have taken three pregnancy tests and all of them were negative. Could I just be going back to my old schedual or do you think something else may be wrong?