Sleep regression?

So my 4 month old son used to be a great sleeper. At about 6 weeks, he started hating naps during the day but would sleep 5-7 hrs at night depending on the day. We decided to move him from the rock and play to his crib and he did great! However, the past 3 weeks have been awful! He is up at 3 am and then every hour after that. If he isn't sleeping in bed with us or on me he wont fall back asleep. At first I thought it was just because he hadnt pooped in 10 days so he was uncomfortable but he went 4 times yesterday finally and still didnt sleep well. Dont get me wrong I am very appreciative that my son actually sleeps for us, but I just dont know how to break the habit of sleeping with us. Any suggestions would be fantastic!