My employers disability co UNUM denied my disability before it became long term. My dr says I am. .

I am disabled and my medical records and a letter from my doctor went to my employers disability insurance UNUM. UNUM denied me now twice saying the records don't change their mind. I was on short-term disability for 4 months and now they are denying me. They have never seen me or had a doctor of theirs see me. I am disabled I have been diagnosed with fibromyalgia since2010 and continued to work, I have worked for this company for 32 years and an excellent employee in a manager job. The fibromyalgia became very severe in November 2016 and that is when I went out on short-term disability. Since then the disease has become worse and I can't go back to work. Obviously they will not be able to hold with my job but can they fire me because I am disabled? Would a severance package be able to be negotiated with them since I will be 63 years old in July of this year? I am not being paid by my employer for the last month but yet they have not fired me I feel like my life is just up in the air. They have told me now for the past two weeks so get back to me.