What Causes Spotting In Between Menstruation While On Contraceptive Pills?

Hi there,
This is rather embarrassing, but lately I've been having spotting between period. I'm on Gianvi birth control and my gyno said it was due to that. Now, I have dark spotting every day and just today it was dark brown clumpy discharge? I don't think it's just my birth control. I am sexually active with one partner and use protection. Please Help!