Wage reporting when hours change weekly after 12 years as an electrician's helper

I picked up part-time shifts as an electrician's helper and I am confused about how to report them. I would rather hear the honest version than the polite one. Sometimes my paycheck is late by a week. Did anyone get an overpayment notice from a mistake?

I estimated and then checked my pay stub. When there was a small difference I wrote to the agency to correct it.