White spot on tongue since last 4 years.

Right after cocieving my second child (c section )i had a white patch on my tounge and i went to a dermatologist he told it is lichen planus, then i had medicines for 3 months but nothing worked fr me. After my baby was born i went to another dermo he told it is fungus and for another 6 months i had prescribed medicines. This way 3 years passed but i got no results. Finally i had tounge biopsy which is normal according to doctors and they prescribed me nitrogen liquid gas therapy. I didn't had that therapy. But since 2 months i am having severe pain in having spicy food. That white patch is less and it is more reddish or purplish type. I used too many ointment but no result henceforth I wanted to know what is getting wrong and is it any kind of blood test I need to do or am I need to go for any further test which can figure out for what I'm Suffering from ? Thanks