I was hurt on the job at my 2nd part-time job and not at my full time job.

After being off work for about 6months from both jobs I had to quit my 2nd job due to my injury (I am unable to physically handle both jobs) when it was time to go back to full duty and I am afraid now of losing my full time job.

I need to have back surgery to remove a HNP disc, but I cant because I have used all my FMLA for my full time job. (my boss tells me I am not covered for anything because I didnt get hurt there)

So now, I have to live with excrucating pain until next May/June when I can have my FMLA renewed. What can I do? What rights do I have?