Keep in mind this is no failure on your part.

Is there anyway to gets some respite for yourself? Can you call upon any friends or family members to step in for a night or two to give you a break?

Sounds like you are doing what you can - and a good job - at caring for your daughter's needs. Just don't forget your own. They I believe are equally important. Ensure you are doing some self care. I've had some success with self help books - especially ones that are CBT.