Praise be to Allah.
We ask Allah to heal you and make you well, and to replace your waswas with peace of mind and certain faith.
You should realize that what has befallen you is a great test, and if you bear it with patience and seek reward with Allah for it, you will attain a great deal of good, by Allah’s leave. The Prophet (peace and blessings of Allah be upon him) said: “Calamity will continue to befall the believing man and the believing woman with regard to themselves, their children and their wealth, until they meet Allah with no sins on them.” (al-Tirmidhi (2399).
Al-Tirmidhi (2396) and Ibn Majah (4031) narrated from Anas (may Allah be pleased with him) that the Prophet (peace and blessings of Allah be upon him) said: “The greatest reward comes with the greatest trial. When Allah loves a people, He tests them. Whoever accepts that wins His pleasure but whoever is discontent with that earns His wrath.” So receive the glad tidings of a great reward, in sha Allah, and remember that what you feel in yourself will not harm you, so long as you love Allah and His Messenger (peace and blessings of Allah be upon him) and His religion, and you hate disbelief and its people.
There follows some advice with which we ask Allah to benefit you:
1 – You should be certain that this waswas comes from the shaytan and is not real. How can you be a non-Muslim when you pray regularly, read Quran and listen to useful lectures?
2 – You should remember Allah a great deal (dhikr), so that the shaytaan, who is the source of this waswas, will go away from you. The Prophet (peace and blessings of Allah be upon him) said: “… and He (Allah) has commanded you to remember Allah; and the likeness of that is a man who was being pursued swiftly by the enemy, until he reached a strong fortress in which he found protection; similarly a man cannot find protection from the Shaytan except by remembering Allah.”
3 – You know that the way to treat this waswas is to ignore it, so continue to do that.
4 – You should fill your spare time with things that will benefit you, so that you will not have time to think about this waswas.
5 – You should pray to Allah a great deal and turn to Him, and seek refuge with Him. Look for the times when du’as are readily answered, such as the last third of the night and while in prostration.
We ask Allah to heal you and take away this evil from you.
And Allah knows best.