I lost someone really close, my dearest friend, 25 years ago when I was 18 and I loved in fear of losing someone else again unti I reached 35. It totally controlled my life and I in turn tried to control that of my husband and my kids to try to prevent it happening again.
I ended up having the briefest course of counselling and it helped me tremendously. you need to get this sorted before it goes onto more serious things. It is nothing to be scared of but it wil drag you down more and more if you don't get some help.
As others have said, death is natural and not avoidable, but you may be suprised to find you deal with it better than you could ever have thought. Good luck XXXX