I Have Having Fresh Blood A Tinge Of Darker Color

I have having fresh blood a tinge of darker color coming out of my vagina when having sex or about to begin having intercorse. I am fully lubrcated and experience no pain or discomfort whatso ever, before, during, or after. I am on depo-provera birth control shot for almost 2 years. This bleeding happens every single time I have feelings of arousal and or begin sex