Open Question: Can someone please help me: Office Manager getting paid 8.50?

Okay so first of all I am an Office Manager at a local replacement window company. I do many tasks, I am at the office usually all day by myself with no one telling me what to do i just know what i need to get done. As a office manager i am getting paid $8.50. Does this seem a little low to anyone else? I have worked here for 1 year and we have tried to get other people to work part time but no one else can do the things i do. They all needed to be told what to do 24/7. But anyways. I have been recently diagnosed with depression and sleep problems that my boss is well aware of, because of these I sometimes have the lack of motivation to get to work and I am actually going to the Dr today to get put on some new medicine. My boss dropped my pay from $8.00 to $8.50 an hour becuase i was a half hour late. Is this legit being it is caused by my medical problems? Please someone help me with this... I am concerned I am doing to much for this company and not getting the money I should be. Only serious answers welcomed!!! Thank You