Why am I having a heavy period on birth control pills?

[Nikilll]

I'm using same birth control pills for last 2 years for heavy mensuration and retrograde mensuration and also endometriosis pain. Pills contain ; Desogestrel(0.15 Mg),Ethinylestradiol(0.02 Mg). I'm in 42 days back to back pill treatment. I'm seeing in all website withdraw bleeding was lighters compare to normal mensuration. But I have heavy period during withdraw pill . I need why was happening to me?. September 2018 I had been laprascopic surgery for chocolate cyst 9cm endometriosis 3rd stage . After surgery my period not stopped it's own still now without pill. So I taking pill continuosly same time every day. But still my problem doesn't cure. Still I have heavy period on withdraw bleeding.now my problem is increased compared to last 2 years. I'm really need normal mensuration with birth control pills. Now am taking 3 pills per day with trapic MF 3 per day. But still spotting on if I sit down or walking or urine. Please i need relief from heavy period. This problem was started from my age of 12. I'm 26 years old and virgin girl.

Thank you