As Divine Avenger said, the Hall of Echoes is the final section of D2:ED. You will not be able to return to the fjords or Broken Valley. You can go back to your battle tower, but the teleporter is broken, so you can not get outside on Sentinel Island.
There is a bit of a setback at the end of D2:ED, so I can see where you got the feeling you lost (there is only one ending), but you will be able to make things right at the end of FoV.
