I used to have similar problems and the one thing that solved it was taking sailing lessons. It was bad at first, once on an 8-hour trip I vomited 4 times, but gradually my organism adjusted and these days I rarely get motion sickness.
I've observed that people can experience motion sickness very differently. Some people can be fine for long periods of time before gradually getting nauseous and then take just as long to recover without every vomiting. Other people get sick almost immediately and then after vomiting are completely fine. Some people must look at the horizon in order to avoid getting sick and others cannot avoid getting sick. Some people vomit repeatedly while others only need to do it once.
