Is one who commits an act concerning which he doubts whether it constitutes disbelief considered to be content with disbelief if he pronounces the two testimonies (Shahadatayn), performs ghusl, and prays after his act? And is his repentance valid? Does the matter differ for an ignorant person who may doubt everything? What is the intended type of doubt that permits the act? And is merely engaging in an act, the disbelief of which is doubted, with the intention of repentance, considered contentment with disbelief?

You must turn away from whispers (waswas) and not indulge in them, because that has caused you severe harm. The best cure for waswas, after seeking Allah's help, is to turn away from them. Sheikh al-Islam mentioned that whoever enters Islam with certainty does not exit it except with certainty. He also stated that a Muslim who makes a mistake or errs does not become a disbeliever until the proof is established against him. Nor does one who grew up in a place far from knowledge and was new to Islam become a disbeliever if he denies something of the apparent and well-established rulings, until he learns what the Messenger brought. What you mentioned about doubt, accompanied by fear of falling into disbelief, indicates that you have not disbelieved. Rather, these are whispers from Satan.