Sounds like overtiredness to me too (not only Kailey but now also her Mummy )

6-8 hours is a long time for a little one to go during the night even if they are formula fed and it would be more normal at her age to be waking every three hours or so so don't worry too much about her not sleeping through at the moment.

As for being overtired - I hear you - DD had a stint where she didn't sleep at all during the day and it almost did my head in. Does she have some sort of bed time routine that you are establishing? Like swaddling her tight and darkening the room and playing a CD or whatever works for you? If so then maybe try starting this routine after she has been awake for an hour of two even if she doesn't seem tired (remembering that most kiddies Kailey's age can't go for more than about 2 hours of being awake). And pat her or cuddle her or whatever until she does go to sleep (it may take a really long time - try and stick with it - once she has got a bit more sleep she will then want to sleep more and be a much happier little lady)

Also, there is a really really good program run by ACT Health called First Steps - ring the Maternal Health line in your blue book and they will be able to give you all the details - and it deals specifically with sleep and feeding problems in the first three or four months of your bub's life. Are you joining one of the mother's groups that they organise in your area? The maternal health care nurse who facilitates these will also be a huge resource of information - but for now give First Steps a call - they are incredibly helpful and have great information on things like recognising tired signs so that you can put them to bed before they get overtired.

Good luck