We learn from the Ahaadeeth that Rasoolullaah
صلى الله عليه وسلم used to use one Mudd of water for Wudhoo and one Saa` for Ghusl. A Mudd and Saa` were measurements used in those days.
One Mudd = +- 544ml.
One Saa` = 4 Mudd = +- 2.2lt.
That's 2.2lt of water for Ghusl. 2.2lt of water for a bath. These days, people spend 30 minutes in the shower. Some even spend up to 60 minutes in the shower, wasting water like Shayaateen. The average shower uses 8lt of water per minute. 8 x 30min = 240lt just for one person to shower. Compare that to the Sunnah of 2.2lt. How many people can bath using that 240lt of water, if they bath according to the Sunnah? Round about 109 people. Like a whole army.
The Sunnah is to bath using a bucket. Saves a lot of water.
So, try that. You don't have to bath every single day, with your condition. And when you do bath, use just the Sunnah amount of water, which is approx. 2.2lt of water.
May Allaah Ta`aalaa grant you Shifaa, Aameen.
والله تعالى أعلم