If youre having too much trouble finding the right fit for the shirt, get the one that fits the best where you want it, then go to a drycleaner/tailor shop, they should be able to take out the slack...
I am also in the same boat. I am seperating the military after 17 years with out a retirement. I just turned 36 and ready to start a new career away from what I have been doing. I am an aircraft...