Seems to me like you are not really clear on the various components of juice and how they are impacting you. Juice is made from many things, including nicotine (freebase or salt, salt is less harsh) and PG and VG and flavors. It appears your body does not like one of these things.
You should definitely get the dentist to check your mouth and talk to him about vaping if he knows about it.
Otherwise, You have to do the vape elimination diet. This requires a willingness to DIY (make your own juice.) You start with VG ONLY NO NIC, No mouth sores? Try max VG with a nicotine, well for you I might try a salt, one with "low hit" properties or freebase if you want. Start low and slow and move up on the nic until either mouth sores appear (in which case you back off) or until you get nic satisfaction. .If that is all good, I 'd say add 10% PG your body will let you know if you tolerate it. If you do at all, then you CAN try upping the percentage until you get mouth sores. Then, you know to back off. If you can't handle ANY PG it's fine tor use distilled water up t o 5^ (I say others say 10% definitely not more than 10%) but it will thin your vape.
Finally if you can tolerate a small amount of PG, you start adding flavors. Single flavors only one a at time, and if you can't tolerate PG there are flavor makers who make VG flavors. Your selection will have to be more limited.
All this takes time, patience and paying attention. I sympathize I am PG intolerant (not allergic) and more than 10% gives me unpleasant feelings in my mouth and lungs.
If yo\u really want to vape though this is what you HAVE to do.
Smoking is not healthier than vaping for you .Vaping is FLEXIBLE if you are intolerant to an INGREDIENT there are ways to figure out which one, and manage the problem. LOTS of people do it myself include.
Goad luck with what you decide.
Anna