Please help!? What can I do about back pain?

You should try to address this problem by going to talk to your doctor so they can examine you and advise on a course of action. Once you have some treatment in progress, you should also take steps to sort out the locker issue as you should be aimning to reduce the weight you are carrying. Check you are carrying only those things you absolutely need and use a back pack using both straps tightened so the pack is close in to your back - this spreads the load evenly. Talk to your doctor about the weight training as it is possible that this may be aggravating the situation at the moment.