It is not something easily controlled. It sounds like You might need a new speech language therapist. If you aren’t seeing results. I agree overly Positive-ness can be annoying but their absolutely is no reason for anyone to live in Misery or to have stuttering to control Them. I may only have a mild stutter but I really emphasis to other people that attitude has a Lot to do with how people look at your stutter. And of course as we know tension and anxiety makes those worse. Exposure therapy, which is what your SLP trying but it sounds like not succeeding with, can do Amazing things for confidence. Keep at it. You have a voice, you are heard.