I have been doing alot of thinking about the 3 week stall i keep hearing about. Your liver empties out all the glycogen(sugar storage for fight or flight) with it comes about 8 lb including water. Then you continue to lose wt, the liver I think reestablishes this storage after a short time but you keep losing. This is why people report losing inches and then after stall resume losing wt, Could be wrong this is just my theory. Hang in there, get your protein, it will get better

Hope you are doing well after your surgery.