Nighttime sleep help!

Please throw any ideas my way, we are dying right now!

DD2 is 5.5 months old. She used to wake up about twice a night, sometimes three. Not that it was great, but it was manageable. I would almost always feed her when she woke up (she's still EBF) -- sometimes I'd just rock her without feeding her though. She'd go back to sleep fairly easily and sleep for a few more hours.

For the past few days, however, she's been going down easily around 7pm. She sleeps until about 10p, then wakes up. Then the entire night becomes a battle. She'll nurse, but won't fall asleep. The only way she'll go back to sleep is very "intensive" rocking -- holding her just so, jiggling her gently, while swaying. If we try to do anything else she starts flailing around and screaming bloody murder. It will take 20+ minutes to get her to sleep like this -- and then she usually wakes up once we put her back in her bed. It's like her eyes pop open again and the whole process starts again. We're spending most of the night in this cycle, with her not sleeping for more than 20-30 minutes at a time. Neither DH or I are getting any sleep anymore and we're close to losing it! I'm not nursing her most of the time at night anymore -- usually just at 10p when she first wakes up, and again around 2am (most of the time she doesn't act like she's hungry, but around these times she'll usually root heavily and make it clear she wants to eat) -- so it's not like she's always being nursed to sleep.

We think the major problem is that she doesn't know how to fall asleep herself, right? How do we teach that? Putting her down drowsy but not asleep right now just results in her crying and screaming. I'm not against some degree of CIO, but isn't she too young for it?

Finally -- she is still swaddled right now. Thoughts on how this is impacting everything? We've been trying to keep her unswaddled for naps, to get her used to it, and it's meaning she wakes up really quickly -- napping only 20 minutes at a time or so. When I swaddled her for a nap that afternoon (after 3 20 minute naps unswaddled), she easily slept 2 hours, making me think she still benefits from the swaddle. But, in the middle of the night when she's awake and screaming, she's always straining mightily against her swaddle. (although she she's unswaddled, she just flails everywhere, it's not like she stays calm).

Sorry this is so disjointed, I'm seriously sleep deprived right now, but I'm looking for any ideas. I'm going to be looking into some sleep books, but right now I'm looking for ideas I can put into practice tonight, not something I have to wait a week until I can read a book. Thank you...