Shrinking uterus

I'm having my second MC. My first was only at 6 weeks, so it was basically a really heavy period with some clotting that lasted about 10 days. This time, I was almost 11w when my MC started. My uterus measured 10w on Monday at my appointment. I'm having horrible cramping and back pain now, so I'm assuming it's my uterus contracting and starting to shrink.

Anyone have any experience? About how long did it take for yours to return to the normal size after a MC of 10-11ish weeks?