My son is 4 months old and 14 lbs. We never co-slept. He has always slept in his bassinet. I could get him to sleep by doing the same routine every night, then putting him in his bed. I did the CIO method, but it only took one night. I did it when he was about 8 weeks old I think (can't remember the exact age). I would wake him to eat at 10pm, then he would only wake us once a night & I would have to wake him between 6:30-7am the next day. For the past few weeks, he would wake to eat, and then he wouldn't be hungry for his 7am meal. So I started just putting the paci back in his mouth in the middle of the night when he woke. He fell right back to sleep, not hungry at all. I've read that babies just kind of get used to waking up at night. It's not so much that they're hungry, but they do it out of habit. I completely agree with that. Like jlk51496 said, if my son spits the paci out quickly, then I know he's hungry. But he hasn't done that at all at night. So I'm guessing that it's just a habit to wake. Also, since you co-sleep, I read somewhere (it may have even been on this board) that babies wake up naturally and go back to sleep throughout the entire night (we all do, but we're just used to it). It's really hard to go back to sleep when there's a 24-hour diner sleeping right next to you! HA! It's true. If I lived in a bakery, then I'd be up all hours of the night too.