Anyone who does Cambridge and then moves to another diet will immediately gain a few pounds.
Your body may be reacting to the surgery by retaining some fluid at the site of the incision. How many days di you receive an IV?
Did the doctor approve your diet as a post op diet? If not then maybe follow the doctor's instructions for nutrition and wait a few weeks to be fully healed before starting back on the Cambridge.

Stay off the scale.

Remember you have lost a great amount of weight and that is a lot to be proud of.

I hope you have an amazing recovery and get back to "normal" soon!

Thank you for sharing and take care.