I know how you feel. When I was in high school I felt terrified of saying "here", so I would say it very quietly and raise my hand. But if I were to go back in time I would tell all my teachers that I stutter and being called out in front of the class makes me stutter even more. If you are feeling anxious about it you should talk to them and tell them to not call you out. And in the mean time work on the "H" sound. Start very slowly and focus on the Ee - re sound.