Have you been overextending yourself? When I was a young cat I used to work facilities for 8 hours a day and then shift to washing dishes in a nursing home for 3 hours that night. Weekend come I did the morning shift washing the breakfast and lunch stuff. Did it for a few years while being highly inebriated, many a morning I heaved into the sink, it was what it was. That said, you're invincible then. While I've never taken great physical care of myself, the one shot from Fort Lauderdale to DC was a tough one. I'd chalk it up to dehydration and sleep deprivation. If not that for you, I'd say you got 5 years left, enjoy them.