Hello, I gave birth on November 19, a month has passed. Before that, t…

Hello, I gave birth on November 19, a month has passed. Before that, there was a slight discharge. I went for an ultrasound 10 days ago. They told me there that everything is clean, nothing left in the uterus, but my period will start soon. Three days ago, I started bleeding. But for two days in a row, there have been some clots. Nothing hurts. I am not breastfeeding because my baby did not survive?. I saw the gynecologist after the ultrasound; she said everything is fine. But I don't understand what these clots are, or if it's my period. I've never had this before. Has anyone else experienced this?