go to Target and buy their brand of Dramamine, the 24 hour variety. I tell you the Mrs swears by that stuff, like you, she is neurotic about motion sickness and in 50 cruises we've been on, she's only been sick twice and one of those was for good reason, seh was pregnant with our son at the time.
others swear by ginger pills, she never tried those though.
still others try that patch that sticks behind your ear
Good luck and don't dwell on it too much otherwise you WILL make yourself sick.