Suggest Remedy For Delay In Periods,tender Breasts And Nausea

Hi,My period is almost two weeks late and it is never ever late, I have felt queasy or nauseous for about two weeks and the past week I have been throwing up every morning. I have taken 3 urine tests to see if I am pregnant at home and took one at the doctor today, all negative. I have a headache every night and my breast are very tender. What could it be if I am not pregnant?