My 11 week old was sleeping well, but recently started waking up every 2 hours. Why?

You mentioned that you have an 11 week old little girl who was sleeping pretty well through the night, but has recently started waking up every 2 hours. And you're wondering "Why is this happening?" especially if you've gotten a taste of sleeping through the night, it's really hard when they stop doing that. There's many different things that can disrupt a baby's sleeping pattern. Usually it has something to do with illness, teething, growth spurts, or a change in routine, and I'm not sure if any of those apply to your situation or not, but if they do, those could be the possible issues behind it all. Generally speaking though, at 2 to 3 months of age, most babies haven't gotten into a good routine at that point. They're just barely understanding the difference between day and night, and starting to sleep solid blocks of time. Most babies at this point are sleeping maybe 4 to 6 hour blocks at night, maybe 7 to 8 if you're lucky, and taking sporadic naps during the day, and it's pretty normal for them to still want to wake up at night and eat.

Now she should be getting to the point where she doesn't need extra nighttime feedings as long as she's growing well, but all babies are a little bit different, and I recommend talking with your pediatrician first. They can address concerns about gas and reflux that you mentioned, and make sure that there's not any medical problems that are causing an issue. And if the doctor clears her and gives you the green light for sleep training, then you can try sleep training, which is teaching her how to self-soothe and how to go to sleep without help from you. Babies wake up at night and often look to mothers and fathers to comfort them in the form of cuddling and feeding, and they learn very quickly that when they cry, we respond. And so it's a form of behavior modification. "Crying it out" is a very effective method at teaching babies how to self-soothe. After feeding your daughter, changing her, loving her, and laying her down, right now at this point in time, you can start a modified form of sleep training by giving it a couple of minutes before you respond to her, as long as you're sure that she's safe and she's been taken care of - she's just crying because she wants you, then yeah you can give it a few minutes before you respond. And this begins to teach her that, again, she doesn't get what she wants when she cries, which is you.