Cry-it-out method backfires

Anyone here tried the cry-it-out method but didn't work on their LO? My son is 11 months, husband and I tried the method starting 2 weeks ago. At first things were going well, LO's crying got shorter and shorter till 10 mins he was asleep. But 3 nights ago LO's bedtime got worse... The moment we enter the bedroom (we share a room), he would start crying. At first we were able to pacify him back to sleep, but by the 3rd night it was nightmare - he didn't sleep till 7am! I had to carry him the whole night as he refused to be put down and would cry buckets again... Funny thing is daytime naps he is okay, just the nights. And he would be sleeping soundly till we enter the room. Is it us causing him to behave like this? Should we be sleeping in a separate room? TIA!