Thanks everyone. Had to be the grass because he's definitely back to himself now. Begging, purring, flipping the tail, mrrrt'ing...they're all back. Oh, and head bumping too. And no more throwing up or sad meows or sad looks on his face. Just my bright eyed big boy who wants lots of attention. We got a movie last night so he got to lay on me for at least an hour - which is his most favorite thing in the world to do.