Starfish this sounds like a really difficult situation. You sound like you are doing an amazing job, working, studying and a mother.
I think you should talk to your boss. She sounds like she is very understanding. How long is the temp staying for?
If your boss knows a bit more of the situation you are in, perhaps something can be arranged to help you through it. It's not your fault you things didn't go to plan. Hang in there, hopefully things will improve soon.