sonohysterogram and blood clots

So I had my sonohysterogram on Tuesday morning and the doctor told me to expect some spotting and mild cramping. On Wednesday my cramps were terrible, worse then when I have my period. Those lightened up, but starting last night, Thursday, I started to notice some bigger blood clots. The spotting is VERY heavy and the blood clots this morning were about the size of a nickel. I've never had anything like that. Has anyone ever had this or know if this is normal?