I'm so sorry to hear you're having such a struggle. I know just what you feel like. My daughter Alynta did sleep through for a few weeks, but suddenly stopped for no apparent reason when she was 5 1/2 mnths.
I was just like you exhausted, and started doing the whole pulling her into bed with me, feeding back to sleep etc. and eventually she was in my bed for most of every night. I had absolutely no idea what to do.
When she was around 8mnths a friend loaned me a book called "On Becoming Baby Wise" and after I read that and started implementing it, it changed everything. I was really desparate to get her sleep sorted. Not just for obvious reasons, but also as we had a trip to Melbourne approaching and someone else was going to be with us looking after her while we had to be at a conference. I just knew that would be impossible the way things were.
Anyway, in less than two weeks, she was in a full routine including sleeping through. She actually slept through after a couple nights. Ahh what bliss. I can't describe what a relief the first full nights sleep was!
The book uses a method they call PDF or Parent Directed Feeding and works on the assumption that good sleeping habits and routine are like everything else to a baby and are things that need to be learned. It is similar in some ways to the 'It's Time to Sleep' program, but there are some fairly standout differences too. Both programs aswell as the one that the other Belinda has mentioned already on your forum (Hi Belinda!!) use the Feed, Play, Sleep routine plan. PDF unlike 'It's Time to Sleep' helps you to teach your baby how to go to sleep unaided and 'It's Time to Sleep' (going on what I've read about it) seems to focus more on settling techniques.
Some benfits I see with bub being able to put herself to sleep is that it's far easier to have someone else looking after her if need be and also if she stirs in the night and cries a little then doesn't go back to sleep, you know that there is actually a problem and that you need to tend to her.
Something that maybe helpful to you since you've already done so well with getting her into the daytime routine is that the book teaches you how to teach your bub (well their internal clock anyways) the difference between day and night so she'll then start to sleep through.
These days, Alynta is just 13mnths (today actually) and sleeps 7.30-7.30 then 10.30-12 and 2.30-4.30. She is a very strong willed child, but it's just about basic training. I think without the stuff we learned in the book, we'd be struggling now to handle her, not just with sleep stuff, but in general also.
Anyways, sorry to bore you. Hope things improve for you. If you'd like any more info, just let me know.
Thinking of you.