Praise be to Allah.
We ask Allaah, 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 Ramadaan and the previous Ramadaan, because Allaah says (interpretation of the meaning):
“and whoever is ill or on a journey, the same number [of days which one did not observe Sawm (fasts) must be made up] from other days”
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 Ramadaan and in the previous one, because Allaah 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 Miskeen (poor person) (for every day)”
Ibn ‘Abbaas said: This refers to the old man or old woman who cannot fast, so for each day they should feed one poor person. This was narrated by al-Bukhaari, 4505. The sick person who has no hope of recovery comes under the same ruling as the elderly.
Ibn Qudaamah 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 ‘Uthaymeen said in Majaalis Ramadaan, 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. Allaah says (interpretation of the meaning):
“So keep your duty to Allaah and fear Him as much as you can”
“Allaah burdens not a person beyond his scope”
But instead of fasting he has to feed one poor person for each day.
And Allaah knows best.