dręcząca wątpliwość

All the nagging doubts and the questions could be answered.

You want me to talk away your last nagging doubts.

Until then, there is always nagging doubt at the back of your mind - it might not be Rachel.

In the back of her mind, though, she had one nagging doubt.

He looked very carefully, but found nothing more, which left him with nagging doubts.

I couldn't put words on my nagging doubt for the longest time.

But now there was a nagging doubt in the back of his mind.

One nagging doubt lay in how he had acquired these kids.

Third, and most important, was the nagging doubt in my mind about the whole idea.

It was then that he remembered the nagging doubt at the back of his mind.