Irregular bleeding

I have been having irregular bleeding.  In the last 5 weeks I've bled for 3 weeks on and off. I've had cramping, whether bleeding or not. I've had breast discomfort, headaches, and hot flashes. I am 24 years old.  I've been to the doctor several times and had a pelvic abdominal ultrasound and a transvaginal ultrasound. I am waiting to hear from my doctor on the results.  My doctor has discussed pregnancy or miscarriage, endometriosis, pcos, or hormone imbalance. More than anything, I just want to know what is happening.