Low b12.now ok. wheat senstivity detected, 20 days gluten free diet. everything seems improving but hair fall increased.thinning, very oily scalp?

Be patient: The hair will likely continue to fall until your nutritional status has been fully restored. Thus you need to be patient. Oily scalp however is more a sign of seborrhea unrelated to gluten sensitivity and the usual Rx is an antifungal shampoo although tar shampoo, sulfa lotion etd have also been used.

Find a better DR: What you omit is significant. B12 low? Why?? How treated? "Wheat sensitivity" or did you have intestinal biopsy showing celiac disease? Hair loss and oily scalp are not related to either of these.