M.M.
Tiffany,
I feel your pain! Luckily (just not when your in the middle of it) this is just a phase- the sleeping through the night constantly comes and goes- as the others stated based on developmental milestones and teething. the best advise I can give is that if you had good sleeping success with your old routine- don't change anything! Just keep doing things the same as you were- if your little one was sleeping without needing a bottle- don't start giving him one just because he wakes during this period- keep the room dark, don't talk to him, don't let him play... this has served us well- and we are now on the 18 month night waking disruption.
Good luck- just keep reminding yourself at 4 am that this is just a phase and one day- all too soon you'll want to sit there holding him and he won't let you! <hugs>
M.