Talk to Gynecologist on Irregular Periods

(Unmarried)I've never faced irregular periods in my whole life since October. I've finished my normal peroids on 30 September and again on 10th September i started bleeding again that continued for 22 days. Doctors prescribed me pelvic ultra sound and all hormonal tests and CBC which came normal. I'm a Hypothyroid patient but my thyroid is in control. My doc prescribed me duphaston for 15 days and after that i bled so heavily that i was about to faint but my periods end with in 8 days now it's been 4 days since my periods ended and now im feeling sore breast and cramps. What can be the reason?