So it turns out at least part of the reason why Callum has been such a slobbery cranky mess is because he had five (as in, one - two - three - four - FIVE!) teeth coming in at once. At least, that's how many I've counted while sliding my finger quickly around inside his mouth, while he clamps down on it - since he won't actually open his mouth up for me or allow me to inspect it for more than 3 seconds. It appears to be three lower teeth (two molars! and another front tooth) plus two upper teeth (I believe one is a molar but I could be off).
INSANE IN THE MEMBRANE.
Now that those five teeth have broken through, he seems to be doing a little better and his nose is not NEARLY as runny all the time. Hopefully that means we'll get a small reprieve before the rest of his teeth move in and take over. ;-)