i lied about my age at work

so i got hired as a night shift cashier at this local grocery store. the pay is decent and it's flexible enough for me to keep up with classes during the day, but they're really strict about hiring people who are 18+. when i applied, i was turning 18 in two weeks but my birthday wasn't until after the interview process. so i lied and said i was already 18+ because i knew they'd never hire someone not meeting their age requirement. it's been months since then and everyone at work seems to like me, no one has questioned it. still, every time a coworker asks how old i am or talks about turning 19 soon, guilt eats away at me for that fib. i know it was wrong but i need this job so badly.