Redness inside mouth and skin becom thin

2 days ago, I felt like inside my lips(mouth) there is redness in a particular area, but the next day it started spreading overall inside my mouth. Also it feels like the upper layer of skin inside my mouth is getting removed and it's like white cast and only a thin skin is left and it feels burning inside my mouth There is some mouth ulcer also And the front part of my tongue has few mouth ulcer and it feels like its skin also gets removed. It feels same as when we it extremely salty food and skin of tough get affected. I don't know whether it's due to eating something not correct or the heat in my stomach or its fungal infection. But I can't close my mouth because it's burning out there and if I try to keep it open the thin skin start drying and that also causing pain. Please help me with this