I don't mean to be an ass, but I'm just going to quote what I said in your last post. It covered it all. You should not be experiencing waves of pain while on birth control. Spotting/discharge are both normal.
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Various types of birth control can cause spotting/brown discharge. It's usually harmless, but because you've also been having spontaneous immense pains, I would suggest that you go back to a doctor and switch birth control pills in the case there is an underlying serious problem. I've had the same side-effects while I was on birth control because it's simply your body adjusting to the pill, and it can take up to 3 months for your body to settle down and fully adjust.