PLEASE HELP! Puppy disoriented, acting strange like he has amnesia or something, any ideas?

My 8 month old Shih Tzu started acting VERY strange yesterday after he was groomed for the first time. He is normally very playful and hyper and a little crazy! When I came home from work I found him sitting all alone, in the middle of a room and he wouldnt come when I called him, and he wont walk anywhere (he can walk, but its like he is too tired to do it) He is peeing and pooping, and he will eat and drink when we put the food in front of him. He will see the food ( where i has always been) and act like he didnt know it was there. He won't play with his best friend the cat, who he normally spends all day rolling all over the house with. And he is unusually calm and loving, he wont leave my side. I don't have any idea what could have caused this, the groomer didn't give him anything that I know of.( shes a wonderful lady and we have used her for like 5 years) Any thoughts would really be appriciated. I'm probably going to take him to the vet monday, but I just want to hear thoughts, PLEASE!