How long after stopping breastfeeding can you start again?

A few days. Depending on how long ago you delivered your baby, you can usually re-start breastfeeding within a week or two without difficulty but sometimes women can resume milk production several months or even years after stopping.
It depends. Breastfeeding is based on supply and demand principles. If you stop breastfeeding for 2-3 days, then it is important to drink plenty of fluids, nurse your baby frequently and pump frequently in order to reestablish your milk supply.