Early Miscarriage after a stillbirth

I was supposed to be 7 weeks, but I started bleeding on Sunday. The hospital did an ultrasound and the baby had stopped growing at 4 weeks. We are heartbroken. We had lost our daughter in November to full term stillbirth. Has anyone else gone through both a stillbirth and an early loss? My doctor said it’s highly unlikely that the two happened due to the same reasons. We never got an answer (after extensive testing) regarding what happened to our daughter.