If the doubt is rare, then you can repeat to be sure that you recite properly, but if the doubts are repeatedly happening, then you do not need to repeat nor to care for such repeated doubts because it can be from Shaitan who tries to spoil your worship by creating repeated doubts.
1. Always start your Prayers with seeking help of Allah from Satanic whispering by saying after Takbiratul Ehraam : A’ootho Billah minashaytan Arrajeem أعوذ بالله من الشيطان الرجيم.
2. Try your best to focus on your Prayers and do not let any other thought penetrate into your mind while praying.
3. Remember while praying the grave, the Day of Judgement, The Paradise, the Hellfire and your need to the Mercy of Allah.
4. Pray as if it is your last prayer because every one from us is exposed to death any time.
5. Pray to Allah ( SWT) as if you see him in your heart and talk to him directly.