My son is nine years old the past couple of days he complains that his back hurts sometimes the lower back sometimes his lower side near his buttocks he doesnt have a fever he doesnt have a problem going to the bathroom or pain when he goes no stomach pain ,could it be muscle or something else he does sleep on the couch alot instead of a bed but thats a whole different story . he also plays rough with his brother sometimes maybe he pulled something ? Thank you shannon