I used to have that too. then I had a brush with death. since then I have not feared death.
here be my advice: go visit some people who are on their deathbed. it will be hard at first. keep doing it. talk to them. you will eventually learn to accept death, and no longer have uncontrollable fear.
You probably don't have it. We all go through phases where we start to think about the inevitable things in life, like death. It's natural to be afraid of it. But If you can't get up from the bed in the morning because you're afraid of dying, then you should be worried.