Do I need an attorney to appeal the denial of my long term disability claim with The Standard?

I was on disability for rheumatoid arthritis and fibromyalgia from April 2013 until March of 2014 through The Standard. They dropped my claim in March even though my doctor did not approve my return to work. I was forced to return to a full time teaching position in August of '14 because my disability insurance dropped me. My body didn't not handle the return well and I had to stop working the end of October '14. The Standard approved my short term disability claim but denied my long term disability claim stating that it was a preexisting condition. The return to work in August pushed my diseases to the worst level I've ever suffered from. I wouldn't have / shouldn't have returned to work but was forced to bring The Standard dropping my claim. How do I appeal? Thank you.