If it is must to eat or drink in each gap of three hours and at present there is no way of keeping fast as well as there is no hope of restoring strength for fast then it is lawful not to keep the fasts. However, it shall be wajib to pay fidyah equal to one Sadaqah al-Fitr in return of each fast. Sadaqah al-Fitr is one kilo 633 gram wheat or three kilo 266 gram barley which should be paid to poor and needy ones. Right now if you have no strength of keeping fast, but you may keep it during the days of winter, then in such a case it is wajib for you to make their qaza during the winter days and in this case fidyah shall not be enough. You should solve your case as per the above details.
Allah knows Best!
Darul Uloom Deoband