Severe toothpaste allergy.. any advice?

I think I have had a toothpaste allergy for as long as I can remember but when I became disabled 7 years ago it got drastically worse. I can’t use the majority of toothpastes from the grocery store because they make the inside of my mouth peel off in sheets, my gums and tongue turn bright red and STING, my lips swell up to the point that it’s dangerous and they give me extremely dry mouth which causes bad breath because I’m not producing saliva which has given me a ton of cavities over time. I also get severe post nasal drip and swollen eyes for hours after brushing. The few toothpastes I’ve found that aren’t as bad are Biotene and Colgate Prevident but they are sooo expensive where I live.

I’ve never heard of anyone else having this problem before so I’m reaching out here to ask for advice on what I could do about this and what might be causing it? I’ve tried things like xylitol gum, mouth sprays and mouth wash but they honestly don’t really do much.