Is it lack of thoroughness on the part of the medical profession or is it just plain old "Don't give

My husband died one week ago today after a horribly painful illness that had obvious symptoms for at least 18 months. Of course the symptoms got progressively worse until three months ago when he collapsed and had to be taken to the emergency hospital. He was hospitalized (he and I decided) one year ago with these very same symptoms, had in-hospital testing for ten days and released with no diagnosis. Pretty much told to "quit complaining and get on with your life". Frustrated and not knowing what to tell them to look for all we could do was change doctors, and keep describing symptoms. All this team did was change his diabetes medicine. He continued to work, even the day he collapsed and was so exhausted all the time, I begged him to stay home and rest. He would always laugh and tell me that "the tests didn't show anything, I'm ok." He refused to slow down, even when he could barely eat and he lost so much weight, we had to buy new clothes regularly as his size continued to become smaller and smaller. I'm angry and bitter and I miss him so much. Why are the doctors so careless?
Farrah