Breastfeeding to sleep

I need some help. I think I unintentionally got my baby used to falling asleep at the breast and I don't know how to fix it. I always feed him to sleep at night but I've trying to keep him awake after naps so he gets used to falling asleep on his own and he just will not do it. As soon as I put him down he starts crying and I've tried cry it out and I just can't. His crying gets louder and louder and sometimes he cries so hard he has to catch his breath. Does anyone have suggestions on how to get him to fall asleep on his own?? At night he sleeps 11 hours straight but it's the naps that are killing me. He's pretty much cranky all day because I spend it trying to get him to sleep.