I brought my pump to work. forgotten to bring enough storage containers to pump my milk. after the 1st pump, I pout into storage bag. then can I freeze the container after use (without wash?) for 2nd pump?

Hi! It is ok to add freshly expressed breast milk to the frozen milk that you have expressed earlier (if it is within the same day). Let the freshly expressed milk cool thoroughly in the refrigerator first before adding it to the container with the refrigerated/frozen milk. The main point is not to add warm breast milk to previously frozen breast milk as it will cause the frozen milk to partially thaw. For more information: http://www.mayoclinic.org/healthy-lifestyle/infant-and-toddler-health/in-depth/breast-milk-storage/art-20046350