What Causes Sticky Brown Vaginal Discharge While On Cerazette?

Iv been on the pill for about 7 years. Cerazette. I think I may have had this before but cannot remember. But the day before yesterday I had brown sticky discharge which looked elastic like. Iv had clear elastic discharge before that looks milky but never brown. Which I know is to do with ovulation if it is sticky ? Now today iv just been to the loo and the stickiness has gone but it looks more pinky brown wheras before it was dark brown. I am sexually active with my partner of eight years. The other night we had sex for a lot longer and it was more rough. Not sure if that has anything to do with it? I m in no pain at all. Nothing itches or smells and my last cervical smear was normal which was my first one. (I m 25). Thanks.