After walking for 15-30 minutes+ I experience pain in my lower back and knees. Are there any exercises I can be doing to relieve this pain? I have shoe inserts for lower back pain but they don’t seem to be working.

As long as you have been to a dr and have ruled out any serious issues, then strengthening your core muscles will do wonders to ease your back pain. Your core muscles are the muscles in your torso and abs that support your spine. By having strong core muscles, they hold your spine in better alignment; allowing you to walk, without pain. As far as the pain in your knees it could be weakness that you need to build strength, or it could be the way you walk. You may not be walking/stepping properly so that overtime, the way you walk could be putting pressure on your joints and causing pain. Try doing an internet search for proper walking techniques and try to incorporate those into your walks. I have been wearing skecher shape-ups for a few months and I really like them; my lower back doesnt hurt now when i wear them for walks or even grocery shopping. But before you go and spend $100 on a potential "cure" I would try strenghening the core, making sure there is no physical problem, and making sure you are walking properly with proper alignment.