painful and red tongue

Please advise the cause and cure of a red and extremely painful
tongue it's NOT a yeast infection which I get
frequently after antibiotics, this is different I've used Daktarin
oral gel and Nilstat drops both to no avail, is too
painful to eat solid foods, I'm barely "surviving" on porridge and
custard & drink a lot of milk.
Could it be a vitamin deficiency if so which vitamin?
Thank you,
Paulini