I had sex on march 4th and had my period on march 14th. Usually my period last 4-5 days, I had my period for 3 days and it stopped. 3 days later I started bleeding again for 1 day. I also have been feeling lightheaded, nausea , dizzy, very tired, trouble sleeping, and lower cramping. Could I be pregnant?? I had my tubes tied back in 1999. Please help