Accident at work

I had an accident at work, slipping and falling heavily on my back. I’ve been signed off work for 3 months now and finding it hard. I was initially diagnosed with a soft tissue injury, but further tests identified a vertebral fracture. I’m in constant pain when walking, standing or sitting unsupported and don’t sleep well as every time I turn, the pain wakes me up. Added to this, I now have anxiety and depression. Added to this, I am a cancer survivor and have been free of the disease for 7 years. I’ve also been diagnosed with stage 3 kidney disease, osteoporosis, hiatus hernia and GERD. I also have mild osteoarthritis in spine. 
I’m 63 and have had to continue working as state pension age moved to 66 and I had years out of work to raise my family. 
Just wonder if anyone can offer advice as unsure whether I can return to work , as don’t feel well enough physically or mentally. I have a very demanding job. My GP still continues to declare me unfit for work, but unsure how long this can continue. 
I don’t suppose I would meet the criteria for an ill health pension, even with chronic conditions? My accident has turned my life upside down and feeling stressed about the future. I cry every day and have had very little support from my employer, in fact they don’t make contact with me. 
I am in a union, but not received advice, as yet. 
Thanks.