What Causes Reddish Brown Vaginal Discharge Post Intercourse?

I finished my period on Thursday 15 I was intimate on the 16th & afterwards after I peed when I wiped a little blood was there. Saturday I can't remember how I peed but on Sunday after intercourse my boyfriend noticed a brownish mucus on my panty. Monday morning after I pee more brownish mucus was there when I wiped. Today in the morning when I wiped there was more reddish-brown mucus & right now it's like my period starting again.