First of all, congratulations on your progress! That is amazing!!
Second, I echo @Saxons. Even if you have hit your protein goal every single day since surgery, muscle loss is an inevitability. Additionally, after having lost so much weight, the way we carry ourselves changes which can lead to new aches and pains as our bodies adjust.
Adding in some weight/resistance work will help build those muscles back up and help your body adjust to its new shape and weight distribution.