Go to God directly for proof of God. Start having a relationship with him and ask him to show himself to you in a way, that you'll know for sure. Start praying and speaking with God daily and nurture that close relationship. You'll get the confirmation that you need.

When fear of death comes, just go in prayer to God with your worries and fears and put it in his hands. Even if you have to do it repeatedly. God knows our fears and is there for us.