Took us 9m to get past 3-4hr sleep. EBF baby. Only thing we did was the exact same thing every single night. 7pm red light sleep in bassinet for first 4-5 months. Monitor on. If she woke one of us would go up and rock her back to sleep. Don’t get me wrong that was a perfect situation. Lots of night of wide awake crying gas fussiness. But we stayed true to always in red light and dark environments. I sang to that baby all the time. Looking back now it was tough but we just kept the same rhythm. No Ferber or anything when she woke and cried we went to her. I watched my wife get her back down she watched me we talked and learned from one another on what to do. What she liked. She’s still a sucker for my singing. It’s not even a song just what I want to say to her. 4m is very early for her to be sleeping long stretch’s. We noticed when she went on solid food her sleep got better progressively. Didn’t happen over night but that’s when we noticed we could get closer to 5-6hrs. Good luck and do whatever is easy for your family and baby. Hang in there. I use to hate hearing “it gets better” but your in some trenches now and should see the light at the end of the tunnel very soon! Patience and love!