I know everyone recommends different books they swear by, but by the time my 3rd child came along, I really needed somthing that clicked! Someone bought me Secrets of the Baby Whisperer and it CHANGED MY LIFE!!! I think my son was about 9 weeks old when I read it and started the methods, so you can never start too early or too late. It really helps to read through the explanations from the author to get the full idea of what you are doing and why... but the jist of it is called E.A.S.Y.... most parents (myself included) wait until the baby gets fussy and nurse so she can eat, be happy, and fall asleep-- right??
Well, according to this brilliant woman, what you SHOULD be doing is feed her when she wakes up (E=eat)...
Then the baby has awake time (A=activity... which at her age is staring into space and absorbing her surroundings while trying not to get overstimulated)...
Then sleep time (S=sleep)...
Then you get time for yourself (Y=You time)
EASY!
Well, I didn't understand if you were nursing when the child first wakes up, then how do you get him to sleep??? Well, the idea is to remember that when a baby is fussy, it does not mean he needs the boob! I used to make the mistake of offering the boob every time my baby would fuss because I had no idea what else to do! But basically this author tells you to watch your baby's cues. You know you fed her when she woke up, so when she starts to fuss, she is more than likely NOT hungry-- she is getting sleepy. So catch her BEFORE she gets full blown exhausted-- do whatever your baby likes to calm and soothe her. Some like to be rocked, mine liked to be held and bounced up and down a particular way. Swaddle her, then do the soothing thing until the baby is calm but not asleep, then set her down where ever she is going to sleep (ie bassinet or crib)... if she starts to fuss, give her a sec and see if she is just settling in or if she needs to be soothed more by you. If you do pick her up, do the soothing thing (rocking, bouncing, whatever) for as long as needed if she is fussing or crying, but the second she stops fussing, place her back down to sleep. It sounds unbelievably insane but I know it works because I did it myself, but you have to understand that it will not be a miracle thing that will work in 2 minutes. You may have to soothe her, place her down, pick her up and soothe her, put her down, etc over and over and over and over and over and over again. I know you have a 3 year old so it may be very hard to do without her interupting, but I know with my 9 week old I had to pick him up/put him down over 30 times the first night. It took a few weeks and most nights I still had to pick him up and put him down on average about 10 times, but by the time he was a few months old, all I had to do was as soon as he was fussy I would bounce him until he stopped being fussy and then laid him in his crib and he drifted off to sleep on his own -- no boob, no crying it out, no pacifier that would fall out... and he was my best sleeper (still is at age 3!!) of all of my children because he learned very early on how to drift off to sleep on his own, so when he woke in the middle of the night, he would fall right back to sleep-- unless he truely was hungry.
I'm not saying this to be mean, but your daughter will only use you as a pacifier if you allow it. I didn't know any better so I nursed my daughter (my middle child) every 1.5 hours for several months because I assumed every time she cried that she was hungry. Now I know better and my 3rd child was the happiest and most well rested of all of my kids.