As you are describing your pain mainly while standing, it may be because of bad posture of lumbar spine in association with your feet and lower limb alignment. Need to check visibly. And one of the reason on weak core and spinal strength. If your life style is sedentary with no or lack of exercises is will vanish after starting of proper exercises for your back.
Next Steps
Try to reach to your physiotherapist who can help you to find out exact problem and can Fees you with optimum solution.
Health Tips
Use proper foot wear may be sports shoes when you are standing for longer time. Take breaks in between your standing times with little beat of sitting or walking or some stretches.