am i being discriminated against medically?

I work for the transit dept in my city and have been on leave since October 1st for a medical condition with my leg. I had arthriscopic surgery to repair my knee and found out of another condition called lymphedema.I have been going to physical therapy, and my doctor has not released me to return to work yet. My FMLA ran out on Christmas day, and I applied for an extension because my doctor kept me out of work longer, the city declined. I received a certified letter stating that I must return to work no later than Monday, January 7th and provide a doctor's note upon my return. If I do not return to work by then, I would have voluntarily resigned my employment by the 11th. I am not cleared to work, and my employer told me that I am not eligible for unemployment because the job is available for me to come back to next week ,even though he has the documentation from the doctor stating that I am not allowed to work in any capacity right now. What are my options?