My son will be 5 months old on May 16th and I think he has come to the realization that he likes to sleep on his stomach. I put him to sleep on his back every night and when I go to check on him he has already rolled over to his stomach. When I try putting him back to sleep on his back he cries and cries. I know they say babies shouldn't sleep on their back because of SIDS but if he automatically does it on his own during the night I won't know...Please advise...