Fired for FMLA time related to a settled Work comp case

I worked for a local utility company as a repair technician. I was involved in a work injury in 1993. That work comp case settled in my favor awarding me lifetime medical coverage. In 1998 I had shoulder surgury covered by work comp. Over the years it is often neccecary for me to take time off from the physical nature of my job. Most occurances are a day or two. All occurances were approved by the company under FMLA. In Aug 2003 the company says they belived there may have been a 'pattern' of absences and hired an outside investigation agency to follow and videotape my activities. The company never asked me to see another doctor or even let me know that they felt there may be a problem. The videotape was sent to one of the company doctors without my knowledge and that doctor said there apeared to be no evidence of pain. It's too late to make a long story short, but in the end I was terminated and have no idea what my legal rights are. Can you help me?