Sheikh Salman al-Oadah
You should seek refuge with Allah from your misgivings. You should read the last two chapters of the Qur’ân – Sûrah al-Falaq and Sûrah al-Nâs – which are the chapters of seeking refuge.
Then you need to ignore all suspicions that you have – regardless of how strong they are or how close to certainty those suspicions might seem to you.
For instance, when you are wiping your head in wudû’, never ever go back to any act that precedes it. No matter how certain you feel that you forgot something – like inhaling water into your nose – ignore the feeling. Just ignore it.
Likewise, in prayer, if you are reciting Sûrah al –Fâtihah and feel a doubt whether you commenced your prayer with the takbirah al-ihrâm, ignore the doubt. Do not go back and offer the takbirah al-ihrâm, no matter how strongly or certain you feel you left it out.
The general rule you must adhere to is this: If you are at any point in the performance of your worship, you must regard everything that preceded it to have been carried out fully and correctly.
Do not pay devilish misgivings any mind, no matter how certain you might feel that those doubts are true.
Source: Islam Today