I am filing for an appeal on my request for retro social security disability benefits. I need some advice.

I was out from April 2015 to April 2016 but didn't file at that time thinking I would be back to work shortly after my injury. I ended up having surgery in November 2015 suffered depression and went back in April 18, 2016. I was told by Social Security I could file retroactively and did. I was on temporary disabiltity for a while and my doctors had put me out all during the time I was not able to work via doctors notes, disability forms. Social security denied my claim stating I wasn't disabled during the time I was out. I don't understand how they came to that conclusiuon being the doctors had all filled out paperwork stating I was unable to work during that time. I would like assistance on my appeal. I have already filed for it but have not begun to submit anything yet on my behalf. I'd like to know my options and any suggestions/help you can give me. Thank you.