av8tr,
you mention virginia. have you tried diving elsewhere in the spring and summer? here in texas for example, we have a current heading south and with a wind coming out of the south or southeast produces nasty 3-5' seas with very short periods. these type waves get me sick. what are your waves like at different times of the year.? i am no doctor but it seems logical it must be something to do with the wind, type waves, type boat you use, type diet, are doing something in spring and summer making you more tired before you go diving.? being exhausted, eating greasy food coupled with some nasty 5' chop can make many people sick. i use bomine( meclizine) . what we used in the navy. works great. take one hour before getting on boat. no sooner or later.
oh well. thats my 2 cents worth. good luck!
dktexas54