It sounds an awful lot like you have a legitamate psychological condition called, "Abandonment Anxiety". My Father, also a very good looking man, well paid, in great physical condition (a surfer), incredibly intelligent, but some similar symptoms.
I'd really advise you seek some professional counselling about this - if anything, it'll be good to have someone to sit down and talk to about it. Lots of people will probably flame me for this, but hey, mental health is as important to maintain as physical health, if not more so. I'm not ashamed to say that I've seen a psychiatrist before, just like I'm not ashamed to say I've seen a Chiropractor, or been to the emergency room.
take care of yourself dude, you won't be sorry, and I'm sure your girl won't be either.