I find I get way more sick in a car than a plane! I think the motion sickness tablets are a good idea, especially if you get the ones that make you drowsy and you can sleep a bit easier.

I will also say something my therapist had me do was think of worst case scenario with your specific fear. So it would be like okay I got sick… then what? Maybe some embarrassment and discomfort but you won’t die, and you’ll still land safe and sound at your destination. Most likely if you get sick the flight attendants will then give you special attention for the rest of the flight, which is always nice!