Sleep Help!!

I'm a FTM and I've fallen into a horrible sleep habit of letting my baby sleep in my arms for naps and on top or next to me at night. He was sleeping well at night in his dockatot until we got back from vacation and his schedule was thrown off. I was so sleep deprived at night that I gave into letting him sleep on top of me and now he will only sleep in his dock a tot for about an hour and a half when I first lay him down for the night, and will not sleep in it during the day. I'm not a fan of crying it out but I'm desperate for any advice on how to get him to sleep on his own and not in my arms. He will be 4 months old on the 22nd and I go back to work the 25th so I'm desperate to get him into a routine by then! Any advice is appreciated but please refrain from bashing as I already feel horrible about this!