I’ve been where you are. I’m now in my mid-30s and have done a lot of speech therapy. Some things that help: 1. Confidence. Be kind to yourself when you speak to yourself using your inner voice. 2. Reading out loud — it helps your confidence. 3. When I feel a block/stutter I will either roll my worlds into one “wave” or hold a tone (almost like a hum) and let the words roll out. This helps to overcome blocks for me.