Is he only drinking the bottle at night? It is important that you don't start introducing undies at night until you get rid of the bottle, so he won't associate the potty training with something negative (the loss of his bottle). I think it'll be diapers for him at night for a month or so, till he learns to self soothe without the bottle and won't make any associations with the potty training and hence, have a regression on that.
Having said that, you can try giving him half of the bottle before his bedtime routine (bath, etc) and save half of it to get him down. During wakings at night, make sure he has a sippy cup of plain water (not juice or milk, just water) on hand in case he wakes thirsty at night. If he wakes at night crying out for you, go to him, reassure briefly say night night and walk out (so, I'm advicing you to use the wi/wo method, described thoroughly in the Child board of FAQ's, under a thread called Teaching Independent Sleep). He'll cry for you but you have to teach him another way to find comfort when he wakes at night other than the bottle. Try to find a lovey or stuffed animal he likes and show him how to snuggle up with it if he wakes at night (something like Teddy will take care of you...). Wi/wo as much as needed till he stops crying out. He might be awake still but if he's not distressed it means he'll soothe back to sleep byhimself. Once you've managed to teach him how to soothe back to sleep without needing a bottle, taking his last bottle at night willb e much easier. As the week goes by, offer the bottle BEFORE the winddown 50/50, then 60/40, till eventually tehre's only half an oz left of it for going down and then nothing. This has to be a gradual process so he won't put up a fight and it'll be easier for you. During daytime explain him what a big boy he's now, he's not wearing diapers but you still love him and he will always be your baby. Offer him a small reward that only "big boys" get to enjoy, like going to an amusement park or a "grown up" toy. This should encourage him to forget about babyish items and will help you through the progress.
Let me know what do you think of this and if i made some sense (i'm still getting used to the new format so i feel kind of dizzy while posting LOL). Keep us posted to help you through this!
