I know just what you're going through. There's a book called 'On Becoming Baby Wise' which is all about baby sleeping. It teaches a method called PDF or Parent Directed Feeding and works off the idea that good sleeping habits and patterns, like everything else, are something that your baby needs to learn.
We used to have heaps of trouble with our little girls sleeping, but now it's all good. Maybe our story could help a little.
When Alynta about 5 1/2 months she suddenly stopped sleeping through and started waking 2/3 times a night. As a result of this and me getting tired I got lazy and started pulling her into bed with me then we'd both fall off to sleep. The problems really started when she wasn't able to go back to sleep without being in bed with me and without a feed. The tireder I got, the worse the problem got and she began waking even more (anywhere from 3 to 8 times in a night and demanding feeds every time) Both she and I got tireder and grumpier until finally a friend loaned me the 'Babywise' book when Ally was about 8months.
It was such a Godsend and within 1 1/2 - 2 wks, she was not only sleeping through, but was also having structured daytime sleeps as well. It was sooo good to get some decent sleep for the first time in months! It took a little patience especially cause we were starting so late, but if you're desparate like I was, it's well worth the pay off of an amazingly happy and content baby not to mention Mum and anyone else who's around.
Alynta is now 13months and everything is still going great because the book helped us learn and lay some basic foundations but also gave us the flexiblity to adjust to meet her needs.
Hope this helps, would love to know how you go. If you want anymore info, or there's anything I can do, let me know.
I'm thinking of you. Oh and sorry it's so long. smile