Sleep!

Does anyone have any tips on getting my 5 month old to put himself back to sleep? At about 4 months, he became really difficult at bedtime so we resorted to giving him a bottle and rocking him to sleep before putting him down in his crib. He wakes up 3/4 times a night crying and has to be comforted back to sleep usually with a bottle etc. But recently it's taking an hour or more at a time to get him back to sleep as he fusses and screams! Me and my partner are both at our wits end with the sleep deprivation and really need some advice :(