How can I build my horse riding confidence?

Well, I was trotting on Holly and she spooked at somthing in what we call "The spooky corner" as somthings always lurking in there ready to scare the horses. Anyway, she started to gallop around the ring and snorting, I knew she wasnt being , she was scared. I managed to calm her down in a corner but she set of again, this time I wasnt ready and lost my balance, I fell off and from then on I have been tipping forward, shaking, and even saying no to trotting. I can tell my instructor is getting a little en-patient, but you see, she's private and she only has 2 other horses and Brave is the only suitable one, but I fell of him jumping and the same thing happened to me then. I LOVE horse riding and Im brilliant on the ground, I have ambitions and goals but it starting to hit me, will I ever reach them? Can someone please help, before I quit riding!?