I know plenty of people that had WLS and didn't get anywhere close to their goal. In all successes with WLS, it's exercise that works. The fact that you're doing it, you should be sooooo proud of yourself.
If it was me, I'd tell them the truth (that WLS doesn't work without exercise). What success you've had is due to what you've done with your trainer and at the gym. If they have an issue, they just don't understand.
In any case, you are doing awesome and congrats! Best wishes...