Sleep help!

Help! My 18mo has never been a good sleeper despite sticking to wake windows since she was born. She’ll wake anywhere from 1-4 times a night and the only way to settle her is to give her milk. Lately she’ll still whinge and cry after she’s had it so it’s obviously not working for us anymore. I can’t let her CIO as I have other children who get woken up be her whinging. I need to get some sleep though, I’m 6m pregnant and can’t have anymore sleepless nights. Does anyone have any suggestions?