Im afraid to do my back handspring, but I don't know why or how to overcome it.?

I've been cheering for ten years. I can easily do a back handspring. Everyone says it looks great when i do it. I know that i can do it. Im just afraid to go sometimes and i have no idea why. Im supposed to get it by Aug. 15th or i can't be on the team. I want to be on this team so bad and i want to do my back handspring. I've tried to have the coach spotting me back away gradually and i didnt do it when they were gone. I don't like the belt or tumbling into a pit or off a tramp. I will any front tumbling skill without thinking about it. But i can't get myself to go back. I have my standing and running tuck and layout. I don't know what to do. Being on this team means the world to me. Please help!