Red discharge and spotting on Krimson.

I am twenty years old. I have PCOD. i have been taking Krimson-35 for 3 years as per my gynaec's advice.       Since January of this year, i started experiencing spotting and unusual reddish pink (and sometimes brown) discharge in the middle of the menstrual cycle (around the 12th, or 15th day). It has happened every month so far and i also experience a lot of white discharge near the end of my period.      I want to know what's causing this breakthrough bleeding and how i can get rid of it. Is krimson-35 causing this breakthrough bleeding? Because i have been taking it for 3 years. Or could there be another cause? I'd be really grateful if one of you actually tells me in detail what the problem may be. Thank you.