Hello! I am new here, and I have joined to get advice on riding. I started riding about 5 - 6 years ago? And have since owned 3 horses. A 13.3hh mare, Trixie, who I learnt to ride on, she was a grey Welsh pony. Diamond, a 15.2hh bay TB mare, who I did all the basics with, but last year she got colic and lameness so she had to be put to sleep. Now I have a 16hh light grey TB mare, Sapphire. She's only 6 and has not had any jump training before. I have been trying to teach her by lunging her over a jump and doing polework, and she can do that fine, but she won't jump with a rider. She'll do a tiny pole, but that's all. I have been getting pain around my tailbone when I jump, when I get off her and when I've been sitting down and get up. Can anyone offer any training advice? Her tack is in good condition, I had it checked at the start of December when I got her.