There is a reason you kept coming back, why is that, and now 37 yeras, that is a long time luck jo
Are you staying with him because of his heart problems and diabetes? Are you stuck because it is comfortable? These are all things you need to ask yourself. After 37 years, you deserve to be happy at some point in your life right?
Are you staying out of guilt? Is it even a marriage anymore in traditional terms?
Maybe you are scared of the unknown and even though life with him isn't great its something.. But in your post you made it seem you need a change for your own happiness, maybe a trial separation?