Cheer up! Motion sickness is curable. Basically what is hapening is that your brain is getting conflicting signals from the different senses that measure "upright", your eyes, your deep muscle sense and your semicircular ear canals. The brain interprets the garbled info as signs of poisoning and issues instructions to the body to clear out the poison by vomiting - thats my theory.
You cure this, or at least get to live with it by coming to accept the different inputs as normal, or by blanking out the conflict by accepting one input as the master and ignoring the others. This is the basis of the instruction to look steadily at the horizon.
The RAF cure motion sickness problems by subjecting pilots to a carefully graded series of disorientation manoeuvres to build up both confidence and tolerance. As for me, I was initially sick after 20min. This had built up to 40min by the end of basic training. I then came back to England in a small ship through 4 days of a North Atlantic gale. Although sick initially, by day two I was up and about, fully acclimatised, and it stuck with me, more or less, after that
So keep on flying, do the mental thing to accept all the different inputs and it will come right.
Dick Whittingham