As I understand, you have pain in both knees, even during normal daily activities of walking and travelling. Though you are comparatively younger, the knee pain appears to be due to arthritis. This can due to your higher weight. I recommend that you consult an Orrthopedic Surgeon, for a thorough examination and Xrays. You may need certain blood tests to rule out any kind of inflammatory arthritis (eg. rheumatoid or gout).