hi, we also had lots of problem putting my daughter to sleep. she's now 6 mos old & we started sleep training her back in jan when she was 3 mos old. the reason why we decided to sleep train is because the first 3 mos was really difficult & tiring having to rock/carry/sing her to sleep. she would cry/scream/arch her back etc. & it took us sometimes over an hour to settle her. like you adac, my back was killing & i had to go to the physio. we tried cio once (for an hour) & swear will never do it again because my baby startled the whole night. then some of friends introduced us to the book "healthy sleep habits happy child" by marc weissbluth as it worked with their babies. we tried it out... it worked for 2 wks & then came chinese new year & my baby's schedule was all out of whack again. it took us another 1 mos to train, but still we had some difficult nights. was about to give up during that month. then my baby learnt how to roll onto her tummy & would play rather than sleep in her crib. tks to some advice from other mom's in this forum (ie. don't flip her onto her back & just let her be, take away the night light etc.) my baby is sleeping better now. it still takes her about 15-30mins to put herself to sleep, but at least it's much better than before. we just put her into her crib & then close the door. sometimes she'd cry, we'd go in to pat her or hold her a little. once she's settled, we leave her alone again. right now, she's having 3 naps during the day (ranging from 45mins-2hrs) & sleeps from ~8pm-7am.
it's hard work! at times, i also felt a bit unharppy because my friend's babies all seem to sleep well, while my baby is so difficult. our schedule basically revolved around her's. also got a lot of pressures from in-law's about this structured schedule,early bedtime etc. etc. but i just tuned it out.
after sleep training, my husband & i could sneak out for dinner once we put her in. i could also run errands during her nap times. we are definitely happier.
this is just my experience. remember, after having a baby, there will be lots of advice/comments from others around you... just do what you think is best for your baby & your family. good luck!