My period was 16dys late and lasted about 4dys, a day after my period ended i had sex right after i started having brown discharge for about 3dys now?

Normal: The brown discharge is normal. If you're worried you could be pregnant, though, if you are having unprotected sex, you could be. I wasn't sure if that was part of your question as well? Brown discharge is old blood. Old blood can stay in the uterus or vagina for awhile, so likely that brown discharge was old blood from your menstrual cycle that hadn't come out yet.