Yes, this could be very serious. One of our dogs got into some toxic mushrooms last year and exhibited similar symptoms. She required a night of fluids at the vet to flush her system and prevent organ damage.
It might also be something neurological like a stroke.
So I'm afraid your best bet is to see a vet. Even if it's something relatively minor, like an ear infection, you'll need meds prescribed by a vet to clear it up.
Good luck!
