miscarriage still or period?

Jules
So i miscarried a couple of weeks ago (8 weeks although i think baby stoped growing around 4-5) and i have been bleeding ever since 
Last saturday i had an ultra sound and my dr said i have very thin linning so i shouldnt expect much bleeding but then i have been bleeding still ever since. Also on monday i passed about 4 very large tissue like substances (different to the clots i passed when i miscarried) at first i thought it was the sac but i thought wouldnt my dr have seen it still on the ultrasound. 
Also im still mildly cramping. 
Thoughts?