Firefox was very slow using 51% of my resources so I closed and restarted. All my tabs are GONE.

I had quite a few tabs open, but no more than usual. Firefox was responding so slowly and other functions were OK, so tried to close some tabs but it was taking too long. So I closed Firefox. I tried to re-open and got a 'blank' - no tabs or Apps pinned. It said I already had Firefox open but it wasn't responding. So I rebooted the computer. When I opened Firefox again, all the tabs and apps were gone and I don't the the option to pin tabs as apps - it's like I've reverted to an older version but the About screen says I'm current.