What Causes Delayed Periods And Negative Pregnancy Test?

First date of my last menstrual cycle was Apr 2nd and my period is 6 days late. Usually I get my menstrual cycle exactly on time, which is 29 days cycle, maybe one or two days early. We tested the home (first urine in the morning) pregnancy, but it gave negative result but I have the symptoms of breast tenderness, food craving …..etc.

Four months before I undergone a laparoscopy operation (2nd Dec 2010) for an ectopic pregnancy, which result in removal of one of my fallopian tubes (right). Even after this operation, I got my menstrual cycle on time every month. This is the first time, I missed my period for a week. Any suggestions……. Would be great

age=23