He did not fast because of sickness for which there is no hope of a cure, then he became able to fast
Question

I have suffered from chronic kidney failure for years. I used to fast without any problems until Ramadan 1431 AH, when I began to feel exhausted halfway through, and my health declined after that and the kidney failure began to get much worse. So I did not fast Ramadan in 1432 and 1433, and I paid the fidyah for not fasting, based on a fatwa from a famous Islamic website after I explained my situation to them. Please note that I did not consult a doctor about that. In 1434 I fasted Ramadan, praise be to Allah, because I had a great desire to fast after I found out that fasting is the best for my condition and to cleanse the body of toxins, which is the opposite of what I had understood previously.
Do I now have to make up the fasts of the two Ramadans (in 1432 and 1433) that I did not fast, or not? Please note that I am still sick and my condition worsens day after day.
Praise be to Allah.Firstly, we ask Allah, may He be exalted, to grant you good health and well-being. We advise you to be patient and seek reward with Allah, may He be exalted, and to be certain that whatever befalls you of trials only seems to be hard and difficult on the surface, but in reality by Allah’s leave it is something good. 
The one who goes through hardship is not, before Allah, like one who is given well-being, and the one who is sick is not like the one who is healthy, if the one who is sick seeks reward with Allah and is patient, for all things happen by the decree of Allah, may He be glorified and exalted. 
Moreover, the fact that you did not fast during those two years is something concerning which Allah has granted you a concession, and there is no blame on you for that, in sha Allah. Allah, may He be glorified and exalted, says (interpretation of the meaning):
“but if any of you is ill or on a journey, the same number (should be made up) from other days. And as for those who can fast with difficulty, (e.g. an old man, etc.), they have (a choice either to fast or) to feed a Miskeen (poor person) (for every day)”
[al-Baqarah 2:184]. 
And it was narrated from ‘Ata’ that he heard Ibn ‘Abbaas say: (This means) those who find it very hard to fast must give a fidyah (ransom) of feeding a poor person (for every day). Ibn ‘Abbaas said: This has not been abrogated; it refers to the old man and the old woman who are not able to fast; for each day they must feed one poor person.
Narrated by al-Bukhaari (4505). 
The fuqaha’ discussed a case similar to what you mentioned, which is that if a patient for whom it is thought that there is no hope of recovery, or a very old person, does not fast, then in subsequent years becomes able to fast because he has recovered or regained good health and the like, will the fidyah that he paid for previous fasts be acceptable, or must he make up the fasts? There are three views among the scholars: 
~1~
The first view is that he does not have to make them up; rather the expiation is sufficient. This is the view of the Shafa‘i madhhab. 
Imam ar-Ramli (may Allah have mercy on him) said: 
Rather the person mentioned does not have to make up the fasts, if he becomes able to fast later on, because fasting was waived for him, and this requirement is not addressed to him, as is the more correct view in al-Majmoo‘, that originally it was the fidyah that was required of him as an alternative to fasting. 
The author of al-Haashiyah commented on that by saying: 
He does not have to make up the fasts; however he is still required to pay the fidyah.
End quote from Nihaayat al-Muhtaaj (3/193) 
Ibn Hajar al-Haytami (may Allah have mercy on him) said: 
If he becomes able to fast later on, he does not have to make it up, as the majority said.
End quote from Tuhfat al-Muhtaaj (3/440) 
~2~
The second view is it is obligatory to make it up. This is the view of the Hanafis and some of the Shaafa‘is. 
It says in Radd al-Muhtaar ‘ala ad-Durr al-Mukhtaar (2/427): 
When he is able to fast, he must make it up, i.e. the old man who did not fast and paid the fidyah instead. End quote. 
~3~
The third view is that it depends. If he recovers after having paid the fidyah, then he does not have to make it up. But if he becomes able to fast, and he has not paid the fidyah for what he missed in the past, then in this case he must fast. This is the view of the Hanbalis, and was confirmed by al-Baghawi among the Shaafa‘is. 
Al-Bahooti (may Allah have mercy on him) said: 
If he feeds the poor (as fidyah) then he becomes able to make up the fasts… He is not obliged to make them up; rather he has to feed the poor. This was stated in al-Mubdi‘. What this means is that if he recovers before feeding poor persons, then he has to make up the fasts.
End quote from Kashshaaf al-Qinaa‘ (2/310). 
It says in al-Majmoo‘ by Imam an-Nawawi (6/261): 
Then al-Baghawi said: If he becomes able to fast before paying the fidyah, then he must fast, but if he becomes able to fast after paying it, then it may be that the matter is like Hajj, because he was required to pay the fidyah on the basis that he thought that his excuse would remain permanently, then it turned out differently. End quote. 
The view that seems most likely to be correct, in sha Allah, is the first view: that the fidyah is acceptable in place of the fasts that he did not observe because of that excuse, whether he paid it previously or has not yet paid it, and he does not have to make up the fasts. That is because the option of paying the fidyah was required of him at the time when he was suffering the chronic sickness, so he should not move from that to another option. Moreover, obliging him to make up what has passed would cause considerable hardship in some cases, and hardship would dictate moving to an easier option. 
Shaykh Ibn Baaz (may Allah have mercy on him) was asked the following question: 
There is a person who suffered from a chronic illness and the doctors advised him never to fast, but then he was treated doctors in another country and he recovered by Allah’s leave, i.e., five years later. Now five Ramadans have gone by during which he did not fast, so what should he do after Allah has healed him – should he make them up or not? 
He replied: 
If the doctors who advised him never to fast were trustworthy Muslim doctors who have knowledge of this type of sickness, and they told him that there was no hope of recovery for him, then he does not have to make up the fasts and it is sufficient for him to feed the poor instead, but he has to fast in the future.
End quote from Majmoo‘ Fataawa Ibn Baaz (15/354). 
See also fatwa no. 84203
To sum up: you do not have to make up the fasts that you missed during the years 1432-1433, even if you did not consult doctors at that time. It is well-known that kidney disease is a chronic disease and that fasting for a kidney patient usually causes harm and hardship. What matters is the experience of the patient himself. As for asking a doctor, the fuqaha’ do not regard that as necessary; rather they recommend the patient to consult a doctor as a precaution, lest fasting cause him harm. 
Whatever the case, we advise you to consult doctors and ask them every time before fasting. 
And Allah knows best.