my 8 year old cat who has never been sick, has been drooling for the last couple of days. Not normal for him. I inspected his teeth thinking maybe a toothache but didn't see anything. He seems to be eating and drinking. But is very clingy...more so than normal for this major lap cat. I tried looking in his mouth again and think the back of his throat looks red. Sore throat? No swollen glads. Does have a dry nose. Any ideas?