Should I stop going to the gym until my BBL?

   The key in most cases is to not calorie restrict with exercise.  A good strengthening program is likely to improve the result.

Very interesting point. It would be useful to see some pictures.
I am very keen on having my patients very fit by the time of their BBL so I never recommend to stop any fitness.
I would instead suggest to add more carbs to your diet, but this should be done in coordination with your surgeon to make sure your calories are counted.
I hope this will help and I wish you a good day.