Thank you for writing and I'm sorry you're in so much pain.
We cannot examine or diagnose anything for you - that is your doctor's job and I'm sorry he is failing you. Please get a second opinion from another doctor.
You may be having a severe allergy to something or you could have a severe case of geographic tongue -
Geographic tongue is a chronic, inflammatory condition of the tongue (can also affect other areas of the mouth) affecting approximately 3% of the population. It is characterized by discolored regions of taste buds or sometimes even cracks in the surface of the tongue. Geographic tongue will frequently show up after eating any of a range of exacerbating foods, or during times of stress, illness, or hormonal surges (particularly in women just before menstruating). The name “geographic” comes from the map like shape of the lesion. Fortunately, geographic tongue is a harmless benign condition that will not lead to oral cancer or infection
About 10% of all geographic tongue patients may experience mild discomfort or a burning/painful sensation. This sensation is often triggered by sensitivity to cigarette smoke, toothpaste, coffee,or hot, spicy foods. But geographic tongue should not be unbearable so you may not that this condition.
Anon, please seek the advice of an oral specialist rather than your own primary care doctor. Get a referral. Please keep us posted and we hope you feel better soon.