I forget what people call post-cruise lightheadedness but it is common. It should go away within a week or two.
My wife and I had a very rough cruise om a small ship (about 18,000-tons) which we sailed through the North Atlantic. In fact, our itnerary took us from Hamburg to Scotland and then back to Norway, so we crossed it twice. Then we headed north from Norway towards the Arctic circle.
We had rough seas almost every night for two weeks - and my wife was sick most of the time. It was our worst cruise ever, and in fact we didn't even have much to enjoy in terms of ports either. It was supposed to be an adventure cruise, but we saw no whales, no polar bears, etc. Just a huge disappointment.
Sometimes good cruises go bad. There isn't much you can do about it. I do know now that I will never take a small ship in known rough seas again. The smaller the ship the more you feel the motion. A ship as big a Equinox, however, I would expect you did not feel nearly as much (although I do realize you can feel motion on any ship if the seas are rough enough).
The smoothest ship I have ever sailed on is Oasis - I never even felt it tip.
In rough water, the Queen Mary 2 handles high seas, steaming acrosss the Atlantic as 30 knots, amazingly well. But they did a LOT of original hull design on that ship.