5 weeks postpartum

I'm 5 weeks postpartum and I think I've started my first period since having my daughter. I'm currently on day 3 of bleeding on day two (yesterday) I had about 3/4 small blood clots on my pad and then sat down to pee and passed a very large blood clot about the size of a half dollar then passed another fairly large one then today I've passed blood clots all day along with another fairly large half dollar size one I'm crampy and my lower back hurts bad. Blood clots are normal for me during my period but never that big so I'm kind of worrying. Any ideas of this sounds normal?