Just so everyone knows. Your “manager” can't be a dick!
I mean I guess they can be a dick, but here is a cold hard rule. “If your going to be sick I need a Dr note”
The only response to that, or anything like it is “I get sick days, if need be maybe we should talk to HR to see what counts as a sick day?”
You work at a small shop that doesn't really have HR and stuff. “Nope, I be sick! And free lawyer will take this case!”
The key is you need to be willing to leave. If your employer is the only job in town, ask the state if they need monitors in that area.