Hello Sea Crittur:
Several thoughts occur as I read your history of your 'illness'. First, this is probably 'salt water aspiration syndrome', a condition described by Edmonds in almost exactly the same words and phrases that you use. His group found that except for ENT barotrauma it was the most frequently reported illness in the Royal Australian divers. Edmonds, Diving and Subaquatic Medicine, 3rd Edition, 1993.
http://www.scuba-doc.com/saltwasp.html. It can occur with overt aspiration but can also occur with micronized droplets of seawater from your regulator. It most often comes on an hour or two after diving and goes away by the next morning whether treated or not.
Other possibilities that can be ruled out by your history include pulmonary decompression sickness, pulmonary barotrauma, "Key West Diver's Syndrome" (infections from regulators and mouthpieces).
Now, it gets interesting! Consider that this might be the result of multiple shallow dives effectively lowering your complement blood levels causing this picture. One of the causes of post-diving fatigue is thought to be due to the 'using up' of most if not all of your C3a, and C5a,d fractions in your blood by venous gas emboli of multiple shallow dives. This has even been shown to be protective to decompression illness on subsequent deep dives! See
http://www.scuba-doc.com/cmplmnt.html .
It would be wiser to have your complement levels checked than to attempt to draw 'nitrogen' levels, an impossible way to diagnose elevations of inert gas at sea level (due to the off-gassing and partial pressures of 1 atm). If the gas is present in bubble form, they would be inaccessible to the study.
BTW, a good cool beer after a dive is great but not when you also take Ibuprofen. This is a sure way to break down the mucous barrier of the gastric lining and getting either an ulcer or erosive gastritis.
