First time poster here, desperate for advice or general encouragement that I'm doing the right thing. LO is 5.5 months old and we're on day 5 of CIO. We were cosleeping up until now and he was waking up every 1.5-2 hours and HAD to be nursed back to sleep. Night 1 was terrible (cried an hour straight, threw up 12 minutes in, slept 4 hours, ate, slept another 4). Night 2 was worse (cried an hour straight, slept/cried for another hour, slept 2 hours, slept/cried another hour, ate, slept 4 hours). Night 3 was vastly improved (cried on/off for 35 minutes, slept 6 hours, ate, slept 2 hours, talked to his mobile a bit, then slept another 2). We thought we were over the bend but night 4 was worse than night 1! He was HYSTERICAL for an hour before passing out for 4 hours, ate and slept another 4 before I fed him again and brought him in bed with me to sleep two more. I am terrified of tonight and don't know at which point I should give up, a week? Tomorrow? Anyone else have a regression within sleep training?