Question

I was intitally hired at fulltime with a salaried wage. I went back to school and was changed to hourly at $12/hr for 20 hrs a week. My boss does not keep records of how long I work. I work approximately 10 hours extra a week to finish my asigned tasks. I wrote an email saying I agreed to work extra hours without pay when I was offered the deal so that I could pursue my education. My boss agreed. Last week I asked for fulltime work because I dropped out of school. My boss said no because I never finish my tasks on time so she is hiring someone else. It was impossible for me to finish full time tasks in 20 hours. I even gave her an extra 10 hours which she does not acknowledge by not keeping records. I have not given her a resignation letter, but she has told me she is looking to replace me. Has she broken any labor laws? Do i deserve an compensaion for the work I put in extra? I feel I was being set up to fail- is that discrimination? Can I get a severance package?