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I have a 4 1/2 month old who was sleeping through the night 7-8 hours at 2 months.  Since he turned 3 months, he has started waking several times in the night.  Originally, I was rocking him to sleep with his pacifier and would reinsert the pacifier upon nightwakings.  He would fall right back to sleep.  In the past few weeks, we have done modified CIO and done away with pacifier.  We have a bed time routine of bottle at 8:10, diaper, lotion, pjs, and lullabies.  I then put him in his crib drowsy but awake, and he is able to put himself to sleep with minimal crying. He slept throught the night just recently for 3 nights in a row.  I thought we were on the road to success.  However, the past few nights, he has been awaking again and screaming.  I don't give him his pacifier, but I tried to soothe him without picking him up, to no avail.  Last night, I decided to let him CIO with check-ins.  The first time he cried for one hour before falling asleep.  He then slept for an hour, only to awake again.  This time he cried for 40 mins before falling asleep.  I don't feed him because he has been able to sucessfully go 10 hours without a feeding, and I don't want to start another habit.  However, I feel so terrible with him screaming, and I don't know if something is wrong or he just wants my attention.  Am I doing the right thing by letting him CIO??  I'm so confused and feeling depressed more and more each day, doubting everything.  Any helpful advice would be greatly appreciated.  I also wanted to mention that he naps 4 times per day anywhere from 40 mins to 90 mins per nap.  And he is having 6 oz. of formula every 3.5 hours.