You always joke about how your back ache is a “sign of aging“. It could be. But it could also be because you’re just not taking care of yourself. Many elderly people who are fit and strong do not suffer from back pain.
Incorrect posture is a common cause of back pain. When you’re slumped into your office chair the whole day, of course, you’ll get tired and your back will ache by the time you get home. It’s also possible that you’ve strained yourself. If you’re going to lift something, bend your knees, not your waist.