It all starts in the mind. you have formed highways in your mind to function a certain way when you're around people so you will naturally stutter and be anxious because of the way you have been conditioned. Thankfully our minds can be rewired. start speaking things of joy and giving thanks to God if you believe. either way, its a process but you have to really work out your thoughts and mental habits. We seem to train our bodies, progress in our jobs perfecting our skills but often neglect the exercising the mind.