I've had almost the same experience as yours. I went to therapy when i was around 8-9 and it realllly helped me, but it got back and as i got older it kept getting worse. We were not in a good financial situation to go to therapy again till now. Right now my stutter is so bad that i can barely speak 1 or 2 words in 10 seconds. ​ I started therapy again 4 months ago and the therapist was very sweet. I could open up to her and discussed a lot of my problems but none of her methods worked for me. I just left 4 months later and almost 1000$ down with worse stutter than before. ​ But.... The therapist often had a combined session with another guy (around 20-21) so we could get to know each other and share stuff. He said that he really improved in the last 3 months and the doctor even showed me a video of him before he started. So idk, it helps some and doesn't help others. If you can afford it then I'd say go for it.