I was right.
He has two teeth coming in on the bottom front and at least one molar poking through in the back. Another part of his gum on the same side is showing all the signs of a tooth ready to emerge.
I'm hoping this bout of teething ends in the next two weeks and then he'll give us a break until October or so to cut the rest of the primary teeth.
I'm going on 38 weeks, so I really don't want to deal with a teething child and a newborn at the same time!