Bed sharing transition

💙Mia • Cajun & Proud, Conservative, wife to Royce 4.12.14 ❤️, mother to Bennett 8.12.15 💙
Bed sharing mamas, I have a question. Please no negative comments about bed sharing. 
My LO will be 4 months next weekend. We plan to transition hi into his crib by the time he is 6 months. However we've noticed he doesn't seem to sleep very long when sleeping by himself. Also, he HATES sleeping on his back. He will only sleep on his belly or side. Any advice or recommendations on transitioning him to his own crib, and sleeping on his back?