Why am I "stuck" at the same weight after a Gastric Byp?

I had a Rous-en-Y Gastric Byp on July 16th (12 days ago) on a Friday. By the following Monday, I had lost 16 pounds, which was probably just something to do with the surgery. Now, about 9 days after the 16 pounds was lost, I had MAYBE lost 5 pounds. Is it normal for my weight to be so "stuck" so soon after the surgery? Any idea about how long before, say, 50 pounds are lost?