Hello.
I understand that vomiting and pain everytime you brush due to swallowing of toothpaste, must be distressing to say the least.
Without knowing which toothpaste you use, I can assume that there are some flavours and ingredients that some people show less tolerance to. (Fluoride, SLS)
Next Steps
Change the toothpaste to try and understand your physiology better.
Sensodyne makes toothpastes without SLS.
Health Tips
Take a pea-sized amount of Sensodyne toothpaste and see if it changes things for the better.
smile.