13-month old won't sleep through the night!!!!!!!!!!!!!help

[Ashelen]

Hi everyone I have a 13-month-old daughter who is an absolute joy....she is very well-behaved, well-adjusted, and has been hitting her milestones pretty much spot-on. (Ahead verbally, right about on target physically). She is the light of my life, and at about 3 months she started sleeping through the night!!! Wonderful, right? Well now for the past 2 months she wakes up once or twice a night crying or whining. She's weaned off the bottle except sometimes when she wakes up at night we give her a little formula in a bottle to go back to sleep (not every time she wakes up tho). We have tried putting a small amount of rice cereal in it, thinking she was hungry, no go. We've changed her meals....fed her closer to bedtime thinking it would fill her up...we've fed her farther from bedtime thinking her stomach was upset...we've tried only water after a certain time in case the sugar in juice was keeping her up, we've tried giving her warm milk and playing soft music...we've changed the temperatures in the bedroom up and down...all NOTHING. Some nights she will sleep straight through with only a little whining but she'll put herself back to sleep those nights (she's actually very good at soothing herself to sleep normally, just not lately!!!). We've tried writing things down to see if we could emulate the things we did that day and repeat everything to see if she would sleep straight through with no success. I'm pregnant with baby#2 and at the end of my rope...every time she wakes up I'm almost in tears I'm so tired, and I know it's not her fault so it's just led to this undirected frustration. Somebody help...how do I get her to stop waking up 1-3 times a night???? (also, she generally sleeps anywhere from 8-13 hrs a night).