Good advice from fonty #83873.
My own opinion is because of your immobility you could try some isometric exercises to build some muscle-mass before your next fast, which you can do while sitting or lying down. If you do some research on the web, such as.....
You body will feel fitter and stronger and you should then be able to accomplish your goals more easily.
If you can get over the first 3 days of fasting it can be plain sailing thereafter. I also found Paul Braggs book "The Miracle of Fasting"....to be extremely motivating and inspirational while doing so.