Steroids... I bet those just added to the water weight.
When I had my BA earlier this year I weighed 10 pounds more the afternoon after surgery than I did the morning of. With next to no eating over the next few days I was almost 20 pounds up by the Saturday after a Wednesday procedure, from swelling and water and such. And, my surgery was much less invasive than yours. Took almost a month for all of that to settle out for me. I would have to imagine that it would take at least a month for your system to equalize back out, too, especially with the challenges you have on the consumption.
I'm sure that you are doing just fine honey. Your body just needs to recover a little before it can buckle back down.
Other than the loss question, how are you feeling?