When shall I sleep again?

After three nights of no sleep... I'm lookin'/feelin' rather rough. I'm definitely sporting mismatched sweats. I don't understand - one night, she'll sleep from 9 to 7, and then there's a night like last night. We put Chappell down at 9, watched a movie, went to bed at 11 - thinking I'd have at least until 3/4ish (on a bad night). Oh no. She was up at 1. I fed her, put her back to bed, and she was up again at 5. From then on, I had to put Reed on duty. Life in general is just much harder when you're so sleep deprived. Reed doesn't get home till 6:30 or sometimes 7 with the new job... that's a long day if you're running on empty!
I'm struggling... when I went to Publix to exchange some formula (Reed bought the wrong kind), I was talking to the checkout lady (like a deranged fool) about rice cereal, formulas, etc. - she was like "go home, feed your baby some cereal, and go to sleep." I love laid back country moms. They're so different from neurotic, by-the-book moms like me. She said, "I started my baby on rice cereal at three weeks - Never listen to the pediatrician."
Ha!
Tomorrow is our 4 month appointment with the pediatrician. I'm dying for her insight. I'm thinking it's teething and possibly a growth spurt (causing her to eat in the middle of the night). BUT, this baby's 4 months old... officially 17 weeks yesterday... and I thought I'd (we'd) be sleeping consistently by now! Tips from moms welcomed...