Hi! Here's a quick response in case ds wakes up and needs me to go lay down with him. DS is almost 3 and we've always co-slept. However, I can usually get out from under him for the first 30 to 50 minutes of naps and the first 1 to 3 hours that he sleeps at night. The book The No Cry Sleep Solution by Elizabeth Pantley is really helpful in learning some techniques to get all kinds of little ones to sleep better alone. It's even got some suggestions geared toward co-sleepers, although it also addresses main stream crib-sleeping babies and toddlers.
I have the most luck getting out from under ds at night because the first 3 hours of his sleep cycle are the deepest. Learning how to "pop" ds off my nipple when he's almost out or only just falling asleep has helped a lot. I insert a finger when his sucking has slowed (he still nurses to sleep and nurses lots during the night), and can usually get my nipple out of his mouth without getting bitten. Then I immediately put a finger under his chin and apply some gentle pressure while he gets used to the change of pressure in his mouth. Sometimes he still makes sucking motions for a minute or two, and the finger holding his mouth closed helps keep him from trying to latch back on. If he really wants the nipple back, he gets it back until his sucking slows again, then I pop him off again. After a few tries, he generally stops nursing and just sleeps. Then I can ease his head off my shoulder and slide back until he's sleeping by himself. It helps to not jiggle his head much, which always wakes him up. It takes practice.
Putting a small firm pillow against his head, back, belly, or where ever helps him feel pressure and think I'm still there. I also have the most luck getting out from under him if I do it during the first 7 minutes after he's just fallen asleep. That may sound wierd, but yes, I timed it. During the first few minutes, he's still settling in. He stays comfy with whatever position he's in as he's falling asleep then. If I wait until he's been out for 15 or 20 minutes, he seems to notice the sudden change of being disturbed.
We use a baby monitor to track when he stirs, and as soon as he starts to wake up, I go and lay back down with him, usually for the duration of the nap or night. I still end up laying in bed for up to 10 hour a night sometimes, but ds never actually wakes up, he gets to nurse in his (and my) sleep, and he sleeps really well. DH also gets some time with me this way, which is essential!!!
I hope this helps. If I think of anything else, I'll add it. Oh, I know! I try to make sure ds's tummy is very full when he goes to bed so that he doesn't want to nurse for a couple of hours. A really consistant routine for bed and nap helps too. Not that ds naps regularly any more, but he used to when he was your dd's age.
Ok, ds has been sleeping by himself for 2 1/2 hours here, so I need to get ready to go lay down for the night when he stirs.
Don't give up. Different techniques work for different families. Trust your instincts about what you need to do, and you will get it figured out. Really. I absolutely believe that babies and toddlers are better off for the security and attachment of co-sleeping. No baby should have to sleep alone until they're ready. Mine will likely be in bed with us for a few more years, and so far I still love it!
Good luck!
Betzi