I'm trying to figure out when/how I should try to develop a more strict nap schedule for my 4 month old. He sleeps in his crib at night, but only really naps in his swing or on his tummy time mat during the day, and also not for too long at a time. Is this normal? I actually just put him in his crib for a nap right now because he was extremely over-tired and I knew he needed a REAL nap... I assume this is the first step! But any other tips for those who aren't huge nappers?