My baby is now 7 months old, and i pretty much followed the GINA FORD way.
According to her book, if the baby is not sick, and was well fed before he sleeps (substantial enough to help him sleep for a longer stretch in the night), then there could be other problems...which she gave some examples for the following in her book:
1.)wrong sleep association. With the help of this book, my baby is able to go to sleep 'unassisted' most of the time, of course there'll be times when he tried very hard to make himself go to sleep, but if he cannot do so, then I'll carry him for a bit until he close his eyes, i'll put him down right away. But he's pretty much used to sleep on the bed alone. so I guess that's also why when he does wakes a little in the middle of the night, he'd be able to go back to sleep by himself. Moreover, wrong sleep association could also mean depending on the comforter, like pacifiers. If they depend on it, that means once it's lost, they'll wake up screaming for it.
2.) Separation Anxiety or Stranger anxiety - baby between 6 - 12 months have this symptom where they begin to realize they're separate from their mothers, somehow that might cause them to wake in the middle of the night, but for more info, i suggest you to buy this book and have a look, a baby is very complicated, can't just use a few words to describe, because it maybe related to a couple of things altogether, but the book tries to answer all your questions.
3.) Naps at wrong time of the day!!
4.) Excessive milk feeding
4.)Imbalance of solids causing him to poo in the night
I don't think the above will help answer your questions, but I do suggest you to take a look at this book, as it helped answered a loooooooot of my questions, and I've been carrying this book with me ever since my baby was born.
Hope this helps!!!