My 2 year old sheltie acts super weird when he sees other dogs. He whines like crazy probably for being so excited and want to play with the other dogs, but when the other dog wants to play with him, he doesn't know what to do and just keep whining or run around in circle. Sometimes he tries to pee on the other dog or constantly trying to lick their butts or genitalia areas, which is very embarrassing for me. Why does he do that and what can I do? Thanks!