have something on the brain
US /hæv ˈsʌmθɪŋ ɑn ðə breɪn/
UK /hæv ˈsʌmθɪŋ ɑn ðə breɪn/
1.
to be unable to stop thinking or talking about something
:
•
He's been having something on the brain about his new project all week.
•
Ever since she got the promotion, she's had nothing but work on the brain.