I just saw your post and had to write. You see my husband and I have experienced something so similar to what you are currently suffering with right now. There are no words to bring comfort to your loss and I am so sorry you are feeling this pain. One piece of advice or information I wanted to give you is about the shaken baby verdict from the hospital. You write that a caregiver you trusted and who you thought loved your kids had done this terrible thing to your little love, but that she says your child fell off the couch. I found a website that contains so much medical information on shaken baby and one of the things is that the articles there show that a fall off a couch can have the same symptoms as shaken baby. I wanted to write because on top of your grief you are also dealing with betrayed trust. It might be that she is telling the truth about the fall so please see the link just in case. This information still does not erase the horrible suffering and heartbreak - believe me I know, but it may at least provide some answers. Knowing the truth behind what happened to ones child does help as we attempt to heal, though nothing can fill that void in your heart.
http://medicalmisdiagnosisresearch.wordpress.com/2010/09/29/child-atd-reconstruction-of-a-fatal-pediatric-fall/
I hope this helps a bit. You might write the administrator of the link above for more help.