okay, sounds like you need a new NS, but you have already established that.
it sounds to me like you could be overdraining. does your shunt have an anti-syphon on it? I went through 4 different valves before we found one that worked for me. Not sure what hospital you are going to, but you can always try going to the ER and tell them you think you are in shunt failure. They will most likely do a CT, a shunt series, and a shunt tap.
How were you diagnosed with hydro? Was a lumbar puncture done? Was it based off of a CT scan?
Don't give up, keep trucking along and stand your ground.