I know that everyone is different, so I try to take it all in stride and be grateful for the opportunity given to me to regain my life.
I am 1 week out since surgery, and I only lost 8.4 lbs since surgery (10 lbs prior to surgery to equal 18.4 total).
It is also depended on your original/current weight. Heavier person tend to loose more initially (not always true, but it is an observation). Also it maybe dependent on your activity.
Since my Acid Reflux has been giving me grief, I wasn't as active until Saturday, when I went out and walked.
Constipation can contribute to not loosing as quickly also.