taking naps

Sara
My little guy is 6months almost 7 months and will only sleep on me during nap time. If I try to put him down in his pack n play he wakes right back up. He didn't use to be like this. How can I get him back to napping in his pack n play. Also at night he sleeps in his crib so I'm not sure why he lets me put him down then and not at nap time.