Back pain can be caused by a lot of things and one of them can be carrying heavy stuff. For example you could be carrying heavy groceries, carrying your laptop in a bag for work, etc. If you’re grocery shopping and you have a lot of bags, try to use a cart to hold your stuff. If you have to bring your laptop somewhere or something just as heavy as a laptop, try to switch the bag from shoulder to shoulder to distribute the weight. You could also consider getting a rolling bag. If you have anything in your bag that isn’t a necessity, you should take it out to keep your load lighter to help your back.