Suggest Remedy For Soreness In Tailbone

My son is 17 years old, 6 feet tall and 160 lbs. He has no fat on him at all. He rides saddle bronc horses in High School Rodeo. He has problems with his tailbone. He has had a sore from riding the bucking machine and the seam of his pants wore a sore on his butt and the eventually abcessed and burst. We kept it clean and it has healed. Now if he hits his saddle too hard he is pooping his pants. I am sure this has something to do with his tailbone and lower back but do not even know where to go for this problem. I am ordering him a tailbone pad today and thought I would start with chiropractor and X-rays . Please let me know if you have any ideas. I know it is self inflicted but he loves riding bucking horses and I would like to figure something out to help him.