My main suggestion would be vet visit time, since your already doing that... Keep him indoors for the rest of the weekend. Watch his eating and drinking, make sure he's doing both. Watch the litter box to confirm he is urinating and defecating normally. Report all of these findings to the vet when you go.
Is it possible to get in to see a vet any earlier then Monday?
"He is your friend, your partner, your defender, your dog. You are his life, his love, his leader. He will be yours, faithful and true, to the last beat of his heart. You owe it to him to be worthy of such devotion."