Wage reporting when hours change weekly - 9 months and counting

I picked up part-time shifts as a recruiter and I am confused about how to report them. I have been trying to stay organised about it. The form asks for gross earnings, which I do not see until later. Who can I ask without risking my claim?

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