Yeah the scrubbing too hard is what I was thinking about me too. And I would detangle before my hair got seaweedy. I figured that out after a few days though.
I'm not sure what it was but I hope it doens't come back. My hair is def thinner. I was like you, fine hair but lots of it.
When I wash now though just a few hairs will shed so whew I'm back to normal yay!