My answer may shock you, but I'm thankful you're fearful over the thought of dying, because if you weren't, you'd be totally unprepared for the greatest challenge you'll ever face -- the challenge of standing before God.
You see, you and I weren't meant for this world alone. We may think this world is all that matters; we even may go through life (as you've done) without ever thinking about what happens when we die. But that doesn't change the fact that this life is not all, but that we'll live on in eternity once this present life is over -- either with God in heaven, or in that place of utter loneliness and despair the Bible calls hell.
Only one thing will keep us out of heaven, and that is our sin. And because we're all sinners, we have no reason to expect anything but God's judgment and condemnation. But God still loves us and has provided a way for us to be cleansed of our sins. That way is Jesus Christ, who took upon Himself the judgment we deserve by dying in our place. All we must do is turn to Him in repentance and faith, and trust Him alone for our salvation.
I'm thankful your treatment seems to be working. But no matter what the future holds, ask Christ to come into your life today. Then God will take away your fears, because "there is now no condemnation for those who are in Christ Jesus" (Romans 8:1).