Light bleeding? Period already ended?

My period ended a couple days ago. Usually toward the end of it I have light discharge but it's more of a brown color, and that stopped a couple of days ago. Today after having sex I went to pee and when I wiped I noticed a pretty noticeable amount of light pink blood on the toilet paper. I'm not pregnant. This never happens when I have sex or after a period. I'm wondering if it could be the amoxicillin I'm on right now for an ear infection? Or is it something else? Should I see a doc? There's no pain either, just a light amount of blood.