4 month old sleeping

Kelly
How do I help my 4 month old sleep longer during the night!? He'll get a warm bath at 7:30 nursed after that and he falls asleep on my boob I put him in his crib and he'll sleep for 3-4 hours then he wakes up every hour or two hours after that I'm hardly getting any sleep! Please help me ladies!! I feel like he's not getting enough sleep!