Parent here. As a parent, you can only lead a teenage to water, you can't make them drink. I'm a stutterer who finally took my speech therapy seriously in my 20s and got fluent. In my teens, I too had speech therapy. As a teen, I also didn't do the work outside of the therapy sessions. I wouldn't be too hard on yourself about it. Teens are struggling to find their way, and the social complexities are brutal. But if you want to focus on your fluency, do it today.