Passing clots

Ok so I’m 6 weeks pp. everything has been healing up perfect! I had a natural birth with no tarring at all. Well today I started bleeding. Maybe my period? But I’m breastfeeding. Maybe it come back early. Ok. But the bleeding is kinda heavy. I’m filling a pad every three hours (which isn’t bad but super heavy for me) then these huge clots are coming out. Like the size of a golf ball . They are dark. Idk if it’s tissue. I’ve had four of them pass today. I have no cramping at all. No pain at all. No discomfort. I just feel a little bit nauseous. Is this normal? Or has this happened to anyone. My on said it is but it seems kinda weird!