Charlie was exactly the same, slept great from early on til he cut his first tooth at 6months, he then cut one every week (or so it felt) and started waking a couple times a night. Though he's always gone back down no fuss with a bottle or cuddle etc. We've had a rough winter & have had some wake ups where he will just scream, not take the bottle but as soon as upright with cuddle fine til back into bed. We've since figured out it's been an ear ache each time...just a thought but have you had his ears checked?
Other than that I've got no help...sorry.