mama needs sleep!

Sarah
My LO will be 4 months old on Tuesday and I'm about to go crazy. It's been about the last 4 or5 nights, he is up almost every 1/2 hours. He will not settle down- isn't eating each time- but is whining and will fall asleep as soon as I pick him up out of his pack n play. He is swaddled with both arms out, we started the transition from rock n play to pack n play almost 3 weeks ago: 
HELP!