How should I help my baby get on a better sleep schedule?

edited December 2021 in Growth & Milestones

I have a 4 month old and right now she's going to bed between 8:00 and 9:40 ish. She doesn't actually fall asleep until around 11:30 and usually needs help falling asleep. She also hasn't really slept the whole night through. Up until a week ago, she was only waking me up once to feed her. However, now she is back to waking up every 3 (ish) hours. Am I doing something wrong? Is there something I should change?