How long can this possibly go on?????

Okay so Natalie started sleeping through the night (8-10 hrs) when she was about 2 1/2 months old. (Sadie was 13 months old and that was after she cried herself to sleep for about a month, 5 hours a night) We were stoked! So in mid july the girls and I went to Monterey to see my sister Andrea and family. Natalie is very routine-oriented and got upset with me for taking her out of her routine. She has not slept through the night since. And the nights are awful. She wakes up sometimes every 30 minutes to eat. Needless to say I have been getting NO sleep. So Richard and I started sleeping in the other room on 2 twin beds next to each other on the floor. That way we can't hear her cry. It's awful I know but necessary. It's been a week and she is still crying all night. I feel so terrible and hope this doesn't last much longer. She is however, extremely strong- willed! On a side note ~ the doctor said she is probably hungry and we should try some food. We have tried peaches, nectarines, sweet potatoes, and green beans. She loves food! (We don't really do the rice cereal first for very long)