Sorry you are feeling poorly.. but I experienced the same problem, though it didn't last three weeks, thank goodness. Mine lasted about 10 days. I began wearing the motion sickness patches when I cruise. I never needed them while actually on board, but I do have some trouble on the smaller boats (tour boats, tenders, etc.) so I wore them for a cruise when we had a lot of that going on. After debarking, I had only a day or two of mild dizziness. I now wear them every time, and it keeps the dizziness very mild and short term.
Good luck and I hope you are feeling better soon.