Cloudchaser5, I think what you're describing is what many people experience - even if they've never flown an aircraft. Isn't it the case that everyone, at some time in their lives, thinks about their own mortality. Not just in a 'deep 'n' meanful' sense either - I'm talking about maybe driving along in your car at 70 mph being aware that there are hundreds of other cars coming towards you - any one of which could flick out of control and crash head on into you. Perhaps it's that same sort of feeling you sometimes get in the air, flying along, minding your own business when you suddenly think 'what if'?
I believe it's probably perfectly natural - it's only thinking about the risk and maintaining concentration that keeps us alive in such situations. As a low hours PPL(H) I occasionally think those 'what ifs?' - you just end up thinking something like 'well, everyone's got to go sometime' and then you get on with the job in hand.
A bit like all stress really - some of it is essential to keep us alive and kicking, too much, and there can be serious consequences.
My vote is you're perfectly normal (or the rest of us are bonkers too!)
2Sticks