This morning I hand expressed some milk and tonight I did a bit more. This mornings batch is already frozen, and I don't want to use another bag...can I just add the fresh milk to the bag already frozen?
Yes, but you need to cool it in the fridge for a few hours first - you can't add *warm* milk to frozen, because it will thaw the frozen milk for a bit, and it will go off much, much too quickly when you get around to using it.
Hmm, I don't know if you can add fresh milk to frozen milk. I keep the bag of milk in the refrigerator, and add fresh milk to the cool milk, until I have a bag full (usually one more pumping). Then I put the whole thing in the freezer. Maybe give that a shot next time.