Crib help

How do i help my son sleep in his crib? We're working on his room but his crib is ready for him to sleep in. The thing is, I'll put him in it when hes passed out, thats the only way i can get him to stay asleep normally, and he wakes himself up by frailing his arms around and starts screaming. Ive put him in it while hes awake to get him use to it, and he loves it, but once i walk away he starts crying and refuses to go to sleep. Ive been working on this for a couple of weeks, I'm using takingcarababies but im not having any luck. Its like the motion of him going down in his crib when hes sleeping is scaring him awake. What can i do to help him?? Any advice?

#edit

Hes 4 months old and is rolling over so i cant swaddle.