With a lumpectomy you could probably purchase some cheaper aah type bras and put them on by stepping in and pulling up. And I'd wear to bed as it stops the dragging.
Depending on position you might be able to use the half size gladwrap and wrap around your chest then just try to keep top part showering to minimum and use flanel etc for that region. I only had tape over mine which could get wet but if padding yes to keeping dry. Do you have phone number for the breast care nurse so you could call and clarify anything Monday. A shallow bath and flanel to top might be an option too.
And yes...to panadol. If this isnt enough a GP or ED can organise a script for panadeine. I can't believe nothing was discussed with you prior leaving. This is very poor discharge planning. I had an information sheet at least. Hope things go smoothly for you. Kath x