at the back of your mind
US /æt ðə bæk əv jʊər maɪnd/
UK /æt ðə bæk əv jʊər maɪnd/

1.
на задворках сознания, в глубине души
a thought or worry that you have but that you are not thinking about consciously
:
•
The thought of the upcoming exam was always at the back of her mind.
Мысль о предстоящем экзамене всегда была на задворках ее сознания.
•
He had a nagging feeling at the back of his mind that he had forgotten something important.
У него было навязчивое чувство на задворках сознания, что он забыл что-то важное.