Hopelessness

Hi, I’m new to this group and to this site - thank you to whoever sanctioned my admission. I don’t, as yet, have cancer, but I have plenty of familial experience with it. On 14th of June, and 4 days before her 78th birthday, my wife of 54 years died, following a long and debilitating illness. She first began experiencing symptoms towards the end of 2023. In April of 2024, she was fitted with a cardiac pacemaker, but this didn’t relieve her worsening condition. She became unable to climb stairs, experienced general and severe muscle weakness, and developed a vivid violet coloured rash upon her body and face. Eventually, she became so ill that, at the beginning of September, she was admitted into hospital, as an emergency patient. Numerous scans, tests and biopsies later, she was eventually diagnosed as having dermatomyositis, an incurable and progressive autoimmune condition. This is extremely rare affecting, we were told, 1 in 100,000 people - most physicians will never encounter a case; and the majority of the hospital staff had never heard of it. In hospital, my wife’s condition continued to deteriorate, in spite of the care which she was receiving. She then began to lose the ability to safely swallow solid food, due to the weakening of her throat muscles. For many weeks, she received liquid sustenance via an NG tube - a narrow gauge tube which is thrust up the nasal passage and down the gullet into the stomach, thereby by-passing the throat. I do not know just how she was able to withstand this, but she did. 
As this form of feeding was unsustainable in the long term, it was decided that the safest option was to fit a feeding tube through the abdomen wall directly into the stomach. When nothing further could be done after this, she was discharged into residential nursing care - this was at the start of November. Over the course of the following months, her condition became progressively worse, to the point at which all hope of some remission became unrealistic. She passed away, in my arms, during the night of 14th June. 
Throughout all of this, the consultants said that my wife’s illness was due to “cancer of unknown origin,” which is listed as a cause of death. Whilst June was ill, I was at her bedside every day. In the hospital, I stayed overnight with her, sleeping on a camp bed beside her, for six weeks. In the nursing home, I was with her every day, sometimes sleeping on a chair beside her. I feel so guilty that I could not help her more, my one consolation being that I was with her at the end, and that that might have been a comfort for her. I have my daughters, granddaughters and friends, and can get through the days, as a rule. I can exhaust myself and run myself ragged but when I close that door behind me and come into an empty house, the blackness descends. I honestly don’t want to be here, and life ahead now looks very bleak. I’m not alone and countless folk have gone through these emotions, but I’ve come on here in the hope of gaining solace from shared experience - maybe I can even help others. 
If anyone can point me in the right direction in terms of groups to join, I’d appreciate that. Sorry for this verbosity !  
Thank you