D.K.
I don't have any good advice except to say, don't beat yourself up. I beat myself up over my daughter's inabilibty to sleep well as a baby and toddler. I now have a 5 month old son who sleeps wonderfully and I did nothing different. I think that some kids are just programmed to sleep well than others are not. My daughter is now 3 and falls asleep at night by herself and (most nights) sleeps all night, from 8 pm to 6 am. I won't tell you how we did it because we tried everything and it was very stressful and to be totally honest, I think it was all useless and she just had to mature enough to be comfortable by herself and to realize she needed and wanted to sleep.
My son on the other hand has slept great since the day we brought him home. He can fall asleep on his own in his crib and other than waking up to eat, he stays asleep on his own. When he wakes up we hear him on his monitor babbling, but doesn't scream for someone to be there with him immediately.
So, I don't know if this is all that helpful since I know it is stressful, but please don't think it is because you did something wrong.
Good Luck,
D.