I am 15 years old and Have a very bad lower back?

Oh my god. This is no lie. But im 15 too and have had lower back pains for like 3 or 4 years now, and they happen in cases that youve explained in your question.. My parents recommended that i go to doctors or try those mage places. My older brother and dad has had the same problem ever since they were around 10. They reckon its a genetic thing with the males in our family. You should ask anyone else in your family if they had the same problems and what theyve tried out to fix it. I did. But tbh nothing has happened for me so far either. I hope i helped in any sort of way. Good luck.