Metal torture by employer

I am a handicap person have joined a company(KPO) in Feb 2014 since then I am trying my level best to perform equally as the other fit employees but unfortunately fails since than my appraisal and premonition got affected and I am not getting benifit of working hard, after two years of my services the seniors started pressuring me regarding work which result's in bad quality work in 2016 June due to mental pressure I got serious illness and recommended for total bed rest for 6 month's by doctor I have medical insurance (ESIC) which allow me 90 days paid medical leaves in a year after 3 month's H.R team have pressurized me to join the company and threaten to give resignation I was in need of job so by taking risk I have joined the company though they have started pressurizing me again to work same as a normal two handed person do but I also failed to do that many times. Last month my seniors by planning gave me a final notice of improvement in my work but these day's they doubled the torture hense I was unable to perform well which leads to mental dipration stress I am in fear of losing job that value me lot as I am the only earning member in my family, kindly suggest.