Honest answer to you is that, this particular feeling doesn't just disappear into thin air. As such, you will need to gradually take up challenges that will give you little successes at a time. The more successes you gain with speech, the less panic mode your body gets into. To start with, I will say join supportive spaces that will allow you time to build your confidence. While at it, do a little introspection. What has helped you in the past? Do a lot more of those. Toss out all others that haven't helped.