Birth control help!

Hi all, I have a few questions and i figured I could find them out here, but I've been on the pill nortrel for about 4 years now. & recently in the second week of pills, I get heavy creamy white discharge. And I know it's not a yeast infection because there's no syptoms. But when this happens it makes sex painful. I dknt know why it happens and it makes me so upset. If someone has advice or if this happens to them please leave a comment. I appreciate it. Thank you.