a few wks ago my 18 month old daughter woke up about 1 am crying for a bottle, i tried to just put her back to sleep but she just keeped crying and i eventually gave in around 3am (i still had to get up for work and needed some sleep) but she is now doing it more often, not EVERY night but most! does this mean she's not getting something or enough? she eats well through the day and gets a bottle before bed of cows milk, should i still have her on formula to fill her better?