How Do I Get My Baby to Fall Asleep and Stay Asleep in His Crib for a Nap?

My 5 month old falls asleep on his own (crying) in 20 minutes at night, and sleeps ok (wakes up once or twice to nurse). But during the day he won't fall asleep in his crib!!! He'll cry and cry and not go to sleep. If I put him down asleep, he wakes up and cries. I can't get him to nap, so I'm pretty tired myself and I can't get any of my chores done. Have you been though this situation? How did you teach your baby to nap in his crib???

Suggestion:

I really hope you aren't letting him cry it out! Try a shhhh pat. You put him on your shoulder like burping him pat him on the back, firmly but not too hard then go shhhh (like a tap running) passed, NOT into his ear. when you feel him relax put him down but keep going shhhhh. He will close his eyes and you will think he is asleep, he is not he will jerk awake, part of the sleep cycle, keep going. My daughter slept through from 6 weeks using this. You need to keep at it. It will take a while to work, please give it at least a month. It will work.