Have you tried increasing your stamina by walking and standing for longer periods of time? perhaps even gentle movement like stretching - anything to just move more? I purchased an exercise ball to help with balance issues and to continue my PT activities here at home - AND gentle movement.

This is going to be my next big goal - to simply move more & sit less - but it's hard to get motivated with the relentless headache. It'll be easier to get motivated when the weather improves (it's extremely cold and snowy).