Your provider's genuinely mismanaging this and doesn't fully grasp how the medication works.
Sure, some people respond strongly to smaller amounts, but plenty need to climb higher, some all the way to the ceiling. There's a reason it scales up to 15mg.
My suggestion would be pushing higher if you're not hitting your desired results and your body's handling the medication fine. Generally speaking too, bigger amounts tend to correlate with more weight lost overall. Not sure how much you're aiming to lose, but if it's substantial, staying parked at a low amount while the scale barely twitches isn't going to get you anywhere close to that finish line.