I know this is hard to think about right now, but you need to do something, anything to get your mind on somethinge else. I am blessed that my HA never got to this point, due to Gods help, a mother who never gave up on me and examples in my life of what real disease was and what it wasn't.
Even if its a few moments, you need to go outside, look up at the sky, take a deep breath, walk around a bit. Look at the things that are good. If you truly are sick and dying and you need to relish every minute. People who obsess about their situation seldom live through serious disease. My mother had Hodgekins Lymphoma in the 70s when it WAS a death sentence. She had it throughout her body. She kept a positive attitude, prayed and forged on. She was healed of her disease. A lady she knew, how had it far less serious than she did, died, because of her attitude.
I know that sounds harsh, but I have a disease myself that could take my life. I was like you (in my youth) and wasted so much time. I was lucky to have an understanding husband and friends, who never gave up on me. You absolutely need help from someone that isn't a family member. You need someone that can give you an objective view of your life.
If you have had all these tests, you aren't dying. But if you were, really knew it, you would be very surprised how your HA suddenly went away. When its confirmed, yes you are a dying, its a whole different ball game. Suddenly you "get your mind right"
Don't wait for that to happen.