I'm keeping my fingers crossed for the Mom and babies and pray they will be ok.
Having said that, it's beyond me how one could not know if your Yorkie is 2.5lbs or 5lbs
The difference in how that would look is HUGE. I would not need anyone to tell me that!
She looks extremely small and she's very young and should not have been bred now and unless she had grown A LOT, she should not be bred ever!
If you are actually concerned, then you will do the right thing and have this little baby spayed and never let her go through this ordeal again.
Do you plan on spaying her or do you still insist on breeding her again?