Let a mature Christian give you advice about your fear. This is what he wrote on the problem of fear of dying, for a Christian.
"Many of us Christians have become extremely skilful in arranging our lives so as to admit the truth of Christianity without being embarrassed by its implications. We fix things so that we can get on well enough without divine aid, while at the same time ostensibly seeking it. We boast in the Lord but watch carefully that we never get caught depending on Him. Jeremiah 17:9 - 'The heart is deceitful above all things and beyond cure. Who can understand it?'
Pseudo-faith always arranges a way out to serve in case God fails it. Real faith knows only one way and gladly allows itself to be stripped of any second ways or makeshift substitutes... The man of pseudo-faith will fight for his verbal creed but refuse flatly to allow himself to get into a predicament where his future must depend upon that creed being true. He always provides himself with secondary ways of escape so he will have a way out if the roof caves in...
To the man of pseudo-faith [when we shall have nothing but God] that is a terrifying thought, but to real faith it is one of the most comforting thoughts the heart can entertain. It would be a tragedy indeed to come to the place where we have no other but God and find that we had not been trusting God at all during the days of our earthly sojourn. It would be better to [seek] God now to remove every false trust, to disengage our hearts from all secret hiding places and to bring us out into the open where we can discover for ourselves whether or not we really trust Him."
My question to you - has God replaced your deceitful heart with a new heart that beats for Him? If so, then you will trust Him for whatever follows death, though all of us do have some fear as to the manner of our death, whether it will be painful or prolonged. Yet the saved Christian knows that death is but a transition into eternity with their Lord and Savior. The Bible points out that it is the devil who keeps people in fear of death, but that Jesus frees people from that bondage. Read Hebrews 2:14 to 13:1.
The Price of Neglect, A.W. Tozer pp12-14 (Christian Publications Pennsylvania 1984)