Help getting over a few fears?

Just about a year ago now, I had a horse. He was a great big quarter horse who loved to cause trouble, but I kept him all the same. Despite the many, many falls I had off of him. One day, we were riding back to the barn, and when we went through this gate (one we had gone through hundreds of times before, no trouble) for some reason, he bolted. I managed to get him under control, and neither of us were harmed. The next day, the same thing happened, but he started bucking like a rodeo horse as well as galloping all over the place. I was thrown a good 30 feet, cracked my knee, and now I have two huge scars on my arms where the gravel tore my skin off.I couldnt walk for months, and I'm pretty sure I came out with a bad concussion as well. I have a new horse now, and she is absolutely darling. But I have such a problem riding outside now. Whenever we are outside, and she gets the tiniest bit ansty or quick, I have to get off because I start having a panic attack. I know she isnt going to do anything, but I cant help it. I cannot ride with other people because my mare gets a little bit scared when people go head-on, and I cant take the thought of what might happen. I can no longer ride through gates without hyperventilating. It is causing a huge toll on my riding, and I cant show anymore or jump, or really advance much anymore, either. Is there any way to help me get over this stupid fear? Any advice would be amazing, thank you.