Have you spoken to your GP about anti-emetic medication or using CBD oils? I have no idea if it would be suitable for you so you'd need to speak to your doctor. But it's something to consider.
Reducing the nausea may help to reduce your anxiety.
The stop method works for me with intrusive thoughts. I say Stop everytime a thought comes into my head. In the beginning, I would say it about 500 times an episode haha, now I can calm myself much quicker. Try it consistently for a period of time, it may help. Reassuring yourself enables the thoughts, you're still getting the reassurance when you may need to be focused on managing the intensity of the thoughts.
Also have you been tracking your mood and attacks? If you can start to see causes for them, you can start to preempt them and prepare to shut down the thoughts before they come.