thanks for your query, i have gone through your question, the dryness on the ventral aspect of your tongue and floor of the mouth could be because of the decreased salivary secretion secondary to a stone within the gland duct causing obstruction to salivary flow...or it could be secondary to
diabetes, or certain drugs like antihistamines.. consult a oral physician..you need to take mandibular cross sectional occlusal radiograph to rule out any stone... i hope my answer will help you...take care..