On Birth Control, Have Irregular Periods, Weight Gain, Breast Soreness And Enlargement, Spotting, Weird Movement In Stomach, Hpt Negative. Cause?

I m on birth control and have always had regular periods here in the past three months they have been irregular especially this month jus very little spotting and brown I have been gaining weight and my boobs hurt and are bigger and every now and then I feel something move in my stomach And at night time and morning I feel sick but don t puke I have taken a pregnancy test but it was negative pregnant?