It's very common to obsess over death and what can happen.
There are a few methods to free yourself of your anxieties; they are kind of simple-looking, but you'd be surprised how effective they are.
One way is through emotional freedom techniques. Just Google it and you'll find all sorts of information about how to do it for free. You may find results immediately.
The other way is through meditation. It can be transcendental meditation, primordial sound meditation, or any of the various other meditations that quiet your mind and teach you to focus on present awareness. That can break your mind's habit of obsessing over the future.
Deepak Chopra's 7 Spiritual Laws is probably available for free at your library; it's not religious, it just talks about how to look at you and your connection to the universe. It may help you to let go. I'm not a doctor and I'm not claiming to know what I'm talking about... but it seems like you're trying to control something that can't be controlled. Sure, you can take steps to be healthy and improve your quality of life. But trying to control the future is like trying to control the weather. It's easier said than done, but one of the keys to inner peace and joy is to surrender to the universe and let go of the desire to control things. I'm sure the Dalai Lama can say it much better than I can, so you might want to check out some of his books or lectures. Once you let go of trying to control the future, you will feel free to enjoy the present moment, and stop worrying about death.
Good luck!