I have a thirteen year old trail horse that has recently (in the past couple days) taken to bolting on me. He has never tried to bolt on me before this. He bolted on me when I was riding him bareback, and when I tried to one-rein him, I fell off. He proceeded to bolt all the way home. When I caught him, I jumped back on and he was well behaved and respectful.
When I got back to the barn, I round penned him and backed him all over the place, and he was perfectly respectful.
The next day, I decided to do ground work with him, and when I asked him to canter on the lunge line, he tried to jump sideways away from me (I didn't have my lunge whip with me, so he wasn't shying away from that.) and he tripped himself, falling on his side, When he got back up, he had mildly scratched his right hind leg with his left hoof. I rinsed it off thoroughly and doctored it, and it is fine now.
Yesterday, I was riding on the trail with some friends of mine, and he had been wonderful up until the way back. We were about one fourth of the way back, and we were going at a comfortable trot. Suddenly, he shot forward, and I tried to one-rein him, but he slammed me into a low-hanging pine tree. I was pulled back, but once we were clear of the tree, I was able to one-rein him. He stopped immediately, and I trotted him out again, doing a one rein stop every few strides, until I asked him for a no-reins stop, and he halted right away. He was fine for the rest of the ride.
I scraped up and bruised my chin and neck pretty badly, and I am scared to ride my horse because I don't know why he is acting like this. My parents will not allow me to sell this horse, so I am stuck with him. I do think that I am partially causing the bolting because I have always been terrified of going fast, and I would like to get and older, dead-broke horse to get over my fear on. I would also like to know what I can do with this horse to get him behaving.
Thank you so much for any help/advice you can give me!