Last Friday my 8.5 month old was sick 4 times between 9.30-10.30, I took him to the walk in the following morning as he wasn't drinking any extra fluids overnight, by morning he had had some milk and managed to keep it down. He's been fine since and has been eating fine and been okay with his milk. Tonight (Tuesday) he's started randomly being sick again, does this sound like a bug that's just come back or could it be something else?