What Causes Delayed Periods With Symptoms Of Breast Tenderness And Abdominal Cramps?

Hello doctor, my lmp is 6/01/2015 but still I did not get my periods thought am pregnant so went to doctor, got urine and beta hcg test negative, what should I do now, but I experience symptoms like breasts tenderness, bloating, mostly leg cramps and lower abdominal pain in the undes line. what s my problem. Please help me.