Hi! Greetings to you.
Tongue or mouth dryness can commonly occur due to insufficient fluid intake/ vitamin deficiency/anaemia. The feel of enlarged tongue can b due to vitamin deficiency or anaemia. Taking certain medicines can also cause dryness of your mouth/tongue. Since you have been noticing this for the past six months it is better to consult your dentist and get examined to know the exact reason for the same as this can lead to tooth decay.
Meanwhile keep yourself hydrated by drinking lot of fluids and have citrus fruits till your appointment.
Hope this helps.