All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
The treatment of whispers is that you have to repel them, to not pay any attention to them, and not care about them.
Giving in to these whispers will lead you to a great evil and corruption in your religion and your worldly matters.
These whispers are nothing but insinuations of the devil who tempers with you. So you must repel them totally and not give any attention to them.
If you doubt whether or not you have been stained with impurity, then act according to the principle, that you have not been stained with impurity.
Anything which you doubt about, just ignore it, and know that this is the religion of Allah that He ordained you with and legislated for you, and that you are not held accountable for neglecting those whispers on the Day of Judgment; rather, you are rewarded for it.
You do not purify anything which you believe that it is an impurity that stained you unless you have absolute certainty, a certainty upon which you can swear, that you have been stained by it. Avoiding impurity for the validity of the prayer is a matter upon which the scholars differed in opinion. Some scholars are of the view that it is a Sunnah to do so, while the majority of the scholars are of the view that it is an obligation to do so.
You may act according to the view that it is a Sunnah, as long as you are affected with whispers until you are spared from them.
We ask Allah to heal you from them.
For more benefit, please refer to Fataawa 381213 and 386326.
Allah knows best.