I am a hoist technician and i hurt by back at work my company sent me to the docter and told him to not book me off. He just gave me pain medication and did not do a propper exam to see what is wrong and did not give feedback when asked what is wrong with my back. Then after 2 months that my back did not get better they sent me to a specialist and told them the same not to book me off. She then told them she will decide when she can see what is the best for her patient( which is me) she the booked me off for a week and put me on light duty for a month. I then gave in the letter at my work place and took my week off to recover. After my week off the sent me a notification  of a hearing that i must attend to assess my performance in the companey where in they said that there is no such thing as light duty in the company, and then said they will get someone to come and assess what light duty is at my company that was almost a month ago i have never been on light duty still going to sight and doing normal work as they expect from me. Still no one was at my workplace to come and assess what light duty is for me at the company and now they want to talk to HR about my performance in the company  as they say i am on purpose stalling work and working slow on sight but when going to sight it is me and one other co worker but sending others to sight it would be 5 workers going together. What can i do to defend myself and protect my job?