I'm 13 Weeks Postpartum, And Have Been Experiencing Dark Brown

I'm 13 weeks postpartum, and have been experiencing dark brown discharge, it came with some mucus and a small clot.

I had unprotected sex with the hubby at my 6 weeks, and he -accidentally- ejaculated inside of me.

I had a period shortly after, and we've had unprotected sex since. But he pulled out.
I didn't keep track of when we had sex or when I had my period.

I've been feeling nauseous the past week, with headaches and fatigue and slight cramping. I thought maybe it was just my period coming.
I'm unsure now, that I've had this discharge.

I guess my question is, is it normal to have discharge so long after a normal, natural delivery?