First of all, your child does NOT have sleep issues. It is perfectly normal for a 5 month old to not be sleeping through the night, and for a baby that ONCE slept through the night to stop. Ferber does NOT work for all children - even DR. FERBER says this!!! He has gone back to his body of work and admitted that it is not for everyone. But what I do know about the Ferber method is that you can not go back and forth with it. You can't start and stop - it is definitely a progression, and the more times you "start" it, the more you'll be dealing with 5+ hours of screaming.
ANd I have a real problem with a pediatrician that instructs you to start this very intense method of sleep training at only 4 months old. My pediatrician doesn't think that any sleep training should begin before 6 months old! I personally am of the opinion that children can learn without such a fierce method, but that is me. NOt everyone believes you have to put babies in their cribs awake for them to fall asleep. My babies always needed extra rocking and/or nursing to fall asleep, and eventually learned to sleep through the night - without "training" them. They just learned what it felt like to get a good night's sleep since I didn't make them cry it out and cause any trauma (for my babies it would have been trauma - their temperaments are not meant for Ferber or CIO - though it is not necessarily traumatic for all babies). THey also did it when their bodies were ready to do it. I nursed, so they needed to eat in the middle of the night for a while. All babies are different. I love this quote from Dr. Sears: "Babies need to be parented to sleep, not just put to sleep. Some babies can be put down while drowsy yet still awake and drift others need parental help by being rocked or nursed to sleep.
The reason is that while adults can usually go directly into the state of deep sleep, infants in the early months enter sleep through an initial period of light sleep. After twenty minutes or more they gradually enter deep sleep, from which they are not so easily aroused. As you probably know from experience, if you try to rush your baby to bed while she is still in the initial light sleep period, she will usually awaken. Many parents tell me: "My baby has to be fully asleep before I can put her down." In later months, some babies can enter deep sleep more quickly, bypassing the lengthy light sleep stage. Learn to recognize your baby's sleep stages. Wait until your baby is in a deep sleep stage before transitioning her from one sleeping place to another, such as from your bed to a crib or from carseat to bed or crib." Here is a link to his 8 INfant SLeep Facts: http://www.askdrsears.com/html/7/T070200.asp
I have another book for you: THe No-Cry Sleep SOlution by Elizabeth Pantley. It is NOT a quick fix method. She requires you to log your nights and really analyze the situation to see where you need improvement. Then she offers suggestions. SHe also offers suggestions that differ for formula-fed and breastfed babies (because they ARE different - breastfed babies need to eat at night more and for longer!), and she offers suggestions on continuing OR stopping co-sleeping.
Are you against co-sleeping? If that is what is allowing your family (and by that I mean the baby, your husband, and you!!!) to sleep and you are ok with it, then do it. There is a whole other lifestyle out there that differs from your friends and Ferber - and our babies are doing fine! My youngest didn't start co-sleeping until she was 15 months old (hurricane evacuation started it), but it has helped her sleep so much better. She'll grow out of the need. In the meantime, my husband and I are getting more sleep - important, because I am 8+ months pregnant. My son did the same thing- started sleeping with us at about 17 months old, but stopped by the time he was 2. He didn't "need" it anymore. Co-sleeping properly can be a wonderful thing for your family. Here is a page of questions and answers about HEALTHY and BENEFICIAL co sleeping, and how to do it safely, by Dr. Sears. http://www.askdrsears.com/html/7/T071000.asp I'm not telling you to do this; I'm simply trying to tell you that it is OK, even if your friends and family don't do it. SOmetimes you have to do what works for YOUR family, not the typical family.
Again, I have to say that a 5 month old who has stopped STTN does NOT have sleep issues! SHe's perfectly normal! ANd if she's breastfeeding, she has had a change in her nutrition needs and may need to nurse more at night.
It's ok to do things differently than your pedi and friends suggest. Tell them to come to your house and see if Ferber works for your baby!!! They'll likely see what you already know: it doesn't work for her. There are other methods out there that work for different babies. Pantley's method works for many and it is a gentle approach to helping your baby sleep. Reading Dr. Sears can help you see that babies need to be PARENTED to sleep, not PUT to sleep. I always say to people that question why my baby didn't STTN when theirs did: I am a mama 24/7. I don't stop being mama when the sun goes down and it's "bed time". I'd also suggest DR. Karp's Happiest Baby on the Block, though it does deal with younger babies first. But he gives great insight on how babies sleep and how they interact with the world. According to him, your baby is barely "out of the womb" as he believes in a fourth trimester, where babies are getting used to life outside the womb. That might be a great read for you too.
It's ok if your baby needs extra help. She's just different than some. BUT.....she may not be that much different. Your friends' babies and your pediatrician's other clients could very well have had their needs ignored while they were being "trained" to sleep at night.
Different strokes for different folks. If my post offends, I don't mean it to. I just want you to know there are different ways for different personalities/temperaments and different families. THEIR way may not be YOUR way....and your baby may very well be much happier for it.
Good luck, honey. You'll get a lot of different advice on this subject, but I think my ideas are worthwhile. And I know a huge group of women that feel the way I do, and we have very happy babies and happy mamas!!!