The reason your dog always licks you maybe many, it varies by the type of dog you have or even the circumstances. This can be a display or nervousness or happiness. Some dogs lick as a type of affection, some to show they are relaxed, and some may even lick demonstrating they may be tense. If it becomes an obsessive behavior you need to find the reason why.
He given you bunches and bunches of kisses but... My kitty does the same thing.. It could they just love you, like the salt on your skin, a security thing like what their mother did for them or an anxiety. I had a pup who would constantly lick her paw, to the point of a sore, her vet said it wad related to a habit turned into an anxiety.