Is this illness that afflicted me after I quit drugs considered a reward from Allah for my patience, or is it a punishment, and what should I do about it Islamically?

We ask Allah to overlook your past sin and for your repentance to be sincere. The affliction that has befallen you will be rewarded if you persevere, for Allah the Almighty says: "Indeed, the patient will be given their reward without reckoning," and He says: "And give good tidings to the patient, who, when disaster strikes them, say, 'Indeed we belong to Allah, and indeed to Him we will return.' Those are the ones upon whom are blessings from their Lord and mercy. And it is those who are the [rightly] guided." And due to the saying of the Prophet, peace be upon him: "When Allah wills good for someone, He inflicts him with trials." So be patient and seek reward [from Allah] and do not complain, for everything Allah decrees is good for the believer.

As for your abandonment of treatment, it is not correct. Rather, you should seek means of healing by consulting trustworthy doctors and using proven medications, as seeking treatment is a prophetic tradition. You should also recite the Ruqyahs that are authentically reported from the Prophet, peace be upon him.

As for your abandonment of Friday prayers and congregational prayers due to being overwhelmed by obsessive whispers (waswas), we hope that you are excused. However, strive against yourself to get rid of this illness, for Allah helps those who are sincere in their struggle: "And those who strive for Us – We will surely guide them to Our ways."