Cannot Fast Due to Illness: What to Do?
Question

I have many days to make up for missed fasts from the past. Unfortunately, this year I am suffering from a medical condition involving my stomach which makes me unable to fast. I do not know if I will be able to fast in the future (my condition could be permanent). What should I do about this Ramadan and the missed days from the past?
Praise be to Allah.We ask Allah, the Lord of the mighty Throne, to heal you. 
You have to refer to a trustworthy doctor . If the sickness from which you are suffering is one from which there is the hope of recovery, then after you recover you have to make up the fasts that you missed during this Ramadan and the previous Ramadan, because Allah says (interpretation of the meaning): 
“and whoever is ill or on a journey, the same number [of days which one did not observe fasts must be made up] from other days.” [Al-Baqarah 2:185]
But if the sickness is permanent and there is no hope of recovery, then you have to feed one poor person for each day that you did not fast in this Ramadan and in the previous one, because Allah says (interpretation of the meaning): 
“And as for those who can fast with difficulty, (e.g. an old man), they have (a choice either to fast or) to feed a poor person (for every day).” [Al-Baqarah 2:184]
Ibn `Abbas (may Allah be pleased with him) said: This refers to the old man or old woman who cannot fast , so for each day they should feed one poor person. (Narrated by Al-Bukhari, 4505). The sick person who has no hope of recovery comes under the same ruling as the elderly.
Ibn Qudamah (may Allah have mercy on him) said in Al-Mughni, 4/396: 
“The sick person who has no hope of recovery should not fast, and for each day he should feed one poor person, because he is like one who is elderly.” 
Shaykh Ibn `Uthaymin (may Allah have mercy on him) said in Majalis Ramadan (p. 32): 
“The one who is permanently unable to fast and has no hope of recovery – such as the elderly and those who are incurably sick, such as those who have cancer etc. – do not have to fast because they are unable to. Allah says (interpretation of the meaning): 
“So keep your duty to Allah and fear Him as much as you can.” [At-Taghabun 64:16] 
“Allah burdens not a person beyond his scope.” [Al-Baqarah 2:286]
But instead of fasting, he has to feed one poor person for each day. 
And Allah knows best.