eat away at
verb
Definitions
To erode.
Example: The river is eating away at the river bank.
To consume or use up, erode or wear away gradually.
Example: The expenses ate away at our profits.
To cause to feel uneasy, troubled, worried, guilty, or vexed; to bother about something.
Example: Not confessing that I had stolen the money ate away at me until I could no longer sleep.