I don't think it's a very good idea to return to work if you have drains in. If they come out Friday then maybe Monday will be doable.
I had a bilateral mastectomy in March 2012 and I have to say the pain was pretty bad. Hopefully they gave you something for the pain. If not, call your surgeon and get something. I slept in my recliner for 2 months after surgery. My husband called it my "womb". It was the only place I could get any sleep.
As for the expanders, if the pain continues to keep you from sleeping, even with pain killers, you need to call the surgeon. It should not be that bad. Better to call and complain than endure so much pain.
Do not feel guilty about not returning to work. You would do the same for your co teachers...wouldn't you?
I do understand about the bills though and I have no suggestions for that. Try to be kind to yourself though. You are going through a life changing journey.
Sending you warm hugs and prayers. Please keep us posted on your progress.