What Causes Delayed Period With Mood Swing And Breast Pain?

Hi, im 26 I have a 3.5 yr old. And although my periods are a little abnormal they are on time. Ive done and ultrasound and its negative along with urine and blood test. My stomach feels as if its stretching ive been having mood swings body and breasts ache . Frequently urinating and feeling movement at times with pain. What can this be?