How do you report hours that vary week to week?

I picked up part-time shifts as a security officer and I am confused about how to report them. Sometimes my paycheck is late by a week. Who can I ask without risking my claim?

Thanks for writing this out. I went through something close to it last year, and it settled down once I kept a simple log of every call and form.

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