Assalam O Alaikum Wa Rahmatullahi Wa Barakatuh Sister,
I also want to share few hadiths with you before giving an advice.
Abu Sa'id and Abu Hurairah (May Allah be pleased with him) reported that the Prophet (ﷺ) said:
"
Never a believer is stricken with a discomfort, an illness, an anxiety, a grief or mental worry or even the pricking of a thorn but Allah will expiate his sins on account of his patience". [Al-Bukhari and Muslim].
وعن أبي سعيد وأبي هريرة رضي الله عنهما عن النبي صلى الله عليه وسلم قال: "ما يصيب المسلم من نصب ولا وصب ولا هم ولا حزن ولا أذى ولا غم، حتى الشوكة يشاكها إلا كفر الله بها من خطاياه" ((متفق عليه))
Arabic/English book reference: Book 1, Hadith 37
http://sunnah.com/riyadussaliheen/1/37
Narrated 'Ali:
That the Messenger of Allah (ﷺ) said: "
The pen has been lifted from three; for the sleeping person until he awakens, for the boy until he becomes a young man and for the mentally insane until he regains sanity."
حَدَّثَنَا مُحَمَّدُ بْنُ يَحْيَى الْقُطَعِيُّ الْبَصْرِيُّ، حَدَّثَنَا بِشْرُ بْنُ عُمَرَ، حَدَّثَنَا هَمَّامٌ، عَنْ قَتَادَةَ، عَنِ الْحَسَنِ الْبَصْرِيِّ، عَنْ عَلِيٍّ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم قَالَ " رُفِعَ الْقَلَمُ عَنْ ثَلاَثَةٍ عَنِ النَّائِمِ حَتَّى يَسْتَيْقِظَ وَعَنِ الصَّبِيِّ حَتَّى يَشِبَّ وَعَنِ الْمَعْتُوهِ حَتَّى يَعْقِلَ " . قَالَ وَفِي الْبَابِ عَنْ عَائِشَةَ . قَالَ أَبُو عِيسَى حَدِيثُ عَلِيٍّ حَدِيثٌ حَسَنٌ غَرِيبٌ مِنْ هَذَا الْوَجْهِ وَقَدْ رُوِيَ مِنْ غَيْرِ وَجْهٍ عَنْ عَلِيٍّ عَنِ النَّبِيِّ صلى الله عليه وسلم . وَذَكَرَ بَعْضُهُمْ " وَعَنِ الْغُلاَمِ حَتَّى يَحْتَلِمَ " . وَلاَ نَعْرِفُ لِلْحَسَنِ سَمَاعًا عَنْ عَلِيِّ بْنِ أَبِي طَالِبٍ . وَقَدْ رُوِيَ هَذَا الْحَدِيثُ عَنْ عَطَاءِ بْنِ السَّائِبِ عَنْ أَبِي ظَبْيَانَ عَنْ عَلِيِّ بْنِ أَبِي طَالِبٍ عَنِ النَّبِيِّ صلى الله عليه وسلم نَحْوَ هَذَا الْحَدِيثِ . وَرَوَاهُ الأَعْمَشُ عَنْ أَبِي ظَبْيَانَ عَنِ ابْنِ عَبَّاسٍ عَنْ عَلِيٍّ مَوْقُوفًا وَلَمْ يَرْفَعْهُ . وَالْعَمَلُ عَلَى هَذَا الْحَدِيثِ عِنْدَ أَهْلِ الْعِلْمِ . قَالَ أَبُو عِيسَى قَدْ كَانَ الْحَسَنُ فِي زَمَانِ عَلِيٍّ وَقَدْ أَدْرَكَهُ وَلَكِنَّا لاَ نَعْرِفُ لَهُ سَمَاعًا مِنْهُ وَأَبُو ظَبْيَانَ اسْمُهُ حُصَيْنُ بْنُ جُنْدَبٍ .
Grade: Hasan (Darussalam)
Reference: Jami` at-Tirmidhi 1423
In-book reference: Book 17, Hadith 1
English translation: Vol. 3, Book 15, Hadith 1423
https://sunnah.com/tirmidhi/17/1
Now based on your post, I think it is fair to assume that for the most part you have the ability to think and make decisions and therefore don't fall in the category of mentally insane person. If your illness do not affect your ability to reason or consciousness, as appears to be the case in the situation mentioned, then it is obligatory for you to pray and fast. But if you do lose your mind sometimes, and is of sound mind sometimes, then you may be excused at the times when you have lost the ability to think, but when you come back to his senses the excuse is no longer applicable, and you will have to offer the prayer that is currently due and make up the prayers that you missed during the time when you may have lost your mind.
What I said above is taken from a fatwa on Islamqa which I am going to quote below:
It says in Fataawa al-Lajnah ad-Daa’imah (vol. 2, 6/370): Prayer is obligatory upon the individual and is not waived under any circumstances so long as he is of sound mind, because the conditions of accountability are being an adult and being of sound mind. The command to pray is not waived because of loss of a limb or physical faculty, or because of sickness, or similar problems, because of the general meaning of the Qur’an and Sunnah, and scholarly consensus to that effect. But if a person suffers some physical harm and is not able to do all the obligatory actions and essential parts of the prayer, then he may pray according to what he is able to do. End quote.
Based on that, if this mental illness does not affect the person’s reasoning or consciousness, as appears to be the case in the situation mentioned, then it is obligatory for him to pray and fast, because he is still accountable.
But if he loses his mind sometimes, and is of sound mind sometimes, then he is excused at the times when he loses his mind, but when he comes back to his senses the excuse is no longer applicable, and he has to offer the prayer that is currently due and make up the prayers that he missed during the time when he lost his mind.
Source: https://islamqa.info/en/answers/1930...-is-the-ruling
As advised earlier by others, check with your doctor. Get some reports and ask your dad or brother to seek the opinion of a local scholar in this regard. Please don't take what I said as a ruling, I am a layman and have no authority to give any fatwa. I can only share what well reputed scholars have said. Whatever the case may be, know that Allah knows your condition and there is reward for any pain Muslims go through as mentioned in the very first hadith I quoted at the start of my post.
May Allah help you in healing and may Allah make it easy for you to pray and fast! Ameen!
Ma'a Salama