I took a peek at your asked questions...just some tips...you're not likely to get many answers for medical questions...we don't know why there is a pain that starts in your butt...surf board questions probably aren't all that popular in many peoples realm of knowledge...and you've only asked 4 questions...keep going, though. ;) Also...it depends on the time of day, too... Just keep asking and I promise, we'll do our best to answer.
Saw your questions. Not a lot of people know about surf boards. The pain you describe sounds like sciatica-missing or worn cartilage between the bones in your spine. See a nuerologist. One shot in the back and no more pain. Looking at the needle is painful but it doesn't hurt. Honest.