Your post means a lot to me. Your words of reassurance bring comfort to my troubled soul. Thank you very much. The Lord will bless you for this.
I am also amazed you have had encounters with death and still remain unfazed. From my previous experience, I thought people who do not fear death have yet to peer into its scary face. I used to be, like most people, in a state of denial about death. I acknowledged that I was going to die but I always thought of it as an event far into the remote, foggy future. Now I live with the constant thought that death is just waiting to pounce on us at any moment.
Such an awareness of death should make us deny the world and live in renewed commitment to the Lord. But in my case, it just leaves me shaking in fear and renders me almost non-functional. I used to study New Testament Greek on my own and was studying the New Testament using the Greek text with the help of technical commentaries. But now I can't even get myself to continue my studies. The most I can do is to read the Psalms. I no longer attend prayer meetings because news updates of people suffering from serious diseases fill me with dread and fear for days.
Sounds like you're in the process of accepting your mortality.
Everyone goes through this, maybe even multiple times in their life, me included.
Always comes out the same way though, you accept it. You come to the realization that there is absolutely nothing you can do to stop it. It may sound bad, but with it, comes an unexplainable peace. You enjoy life more when you know you're going to die, pushes you to be happy, because you know you aren't go to be here forever, as the expression goes, life is too short to worry.
With the way you say you used to be able to make light of death, the sudden realization you might be close to dying, scared you, and rightly so, you'd be a strange person if it didn't.
You may be familiar with the five stages(Usually tied to grief but it works in a lot of situations)
Denial - You've been through this one already
Anger - I think you're in this one now, hard to tell.
Bargaining - some people skip this one, depending on the situation. If your test comes back positive you'll most likely go through it.
Depression - The worst part, it'll feel hopeless, nothing will matter to you, you'll be at the lowest point you've been in your life. (sorry if I'm being blunt, but sugar coating it aint gonna do you no good)
And finally, acceptance - peace, at last.
Life isn't a pleasure trip, for sure.
Ultimately, I think it all stems from your condition (or fear of one). After your test results come back, positive or negative(I'd like to reiterate to slim possibility of someone missing cancer on 12 biopsies on a prostate, they aint exactly big), I think you'll feel much better. But I aint no therapist, just a normal guy... But sometimes that's what you need.
Pray, and spend time with God, even if it feels like he isn't listening, he is. and he knows whats best for you.
God bless! You'll be in my prayers