How long is it supposed to it take for fluoxetine to get out of breastmilk?

Depends: If the mother stopped taking fluoxetine of any dose (10-80mg), it will take 1-2 months to leave her blood (a blood level of fluoxetine/norfluoxetine can be checked) and until that time it will be in her breast milk and placenta. This in not a reason to stop fluoxetine, speak to your doctor. There is alot of data on infants breastfed while mothers were on fluoxetine.