What Causes A Missed Period,sore Breasts And Stomach Cramps?

38 yrs old,My period was due on May 6th, it s May 8th and no sign of it. Hpt neg. never missed a period. Had an etopic in 1998 and live birth 1999. Boobs a little sore, light cramping, slight left left pain, had left side groin pain after walking at school track. Not sure what s going on. Am I pregnant? Is it another etopic? My doctor says I m not pregnant if the test said I m not. Help