hi there,
sounds like one of a few things could be the culprit...
developmental - has he picked up any new skills lately - rolling, crawling, pulling up, or anything else?
teeth - any chance he's getting some?
illness -any chance he's getting sick?
very early separation anxiety?
definitely sounds like something's bugging him & you just need to ride it out. in the meantime, keep soothing him as you have been when he cries. sounds like he does best when you soothe him in the crib (as opposed to pu/pd). maybe just use a calm quiet voice.
it will pass eventually.