I just started a new job three weeks ago, and I work 9 hours shifts M-F, and every week my boss has asked me to also work that Saturday, which puts me over 50 hours in one week. The job isn't too hard, but I work under an unbearable doctor who speaks down to me all day long for not knowing every single office function perfectly. Being spoken to like a dumb dog wears on me by the end of the day. My boss is never in the office, it's only the doctor and I, so he doesn't really know what the office's environment is like. How do I tell him that he's going to burn me out before I'm there for even a month?