Period for 11 days!?!

I’ve been on birth control for about 5 months (sprintec) and I started taking amoxicillin for a about a week for a tooth infection 2 weeks ago but I recently stopped it about a week ago and had break through bleeding while taking my birth control everyday. I know antibiotics affects birth control but I’ve been on my period for 11 days now, it’s a light flow but it’s enough to have to wear a pad but to little for a tampon