legal to refuse an employee work for off the job injury? dr note saying i can work

My job refuses to let me work even after I produced a Dr note saying I can return. Was told I could return when sprained shoulder is at one hundred percent or sign contract a saying I can't take meds at work. I was not given a chance to prove The injury nor medication would impede my performance(paper work). yet someone with a failed surgery, that was injured on the job, is okay to work(physical labor) and his performance is held to lower standards than others. I cant understand why i was allowed to work as a prepper, with a knife under the same medication, as well as gabapentin for my fibromyalgia was put on light duty, all results from an off the job injury (car wreck), and now im in a less physical job position, had a doctors note saying i could return to work on 7/24/12 and still deny me the right to work. Now they want me to sign a contract saying i will not take my medication as perscribed. The injury happened 7/13/12, and did not start to seriously affect me until 7/23/12, when the inflamation and muscle spasms got so bad i couldnt breathe or hardly move my left arm. I think they are afraid of me claiming for workers comp, because of it worsening at the job. I was told by a friend of mine studying law, that if i am to sign that contract i'm not able to get workers comp because it says i havent been following doctors orders. I will be going in to HR tomorrow to apply for short term disability, but am almost sure that i wont get compensated for any of my missed hours because the doctor okayed me for work on the 24th. And was forced to take a leave of absence. Now it seems like they are trying to force me under duress to sign documents to disregard my doctors orders. It's not logical, Doctors have gone to school for 8+ years to gain the knowledge needed to diagnose and treat patients, why would they attempt to override his decisions? They know my family's financial situations and it feels like i'm being toyed with. I'm being pressured into either signing a document against my will, or let my family suffer because i didnt... Finding a job that pays as well as this one, especially with the overtime during the busy season, would be almost impractical at this point, Ive been tempted to sign the contract, just to be able to see money coming in again. Tomorrow i need to call the KHRA though. I dont want to sign anything without counsel from an attourney though,