I've been having lower back pain after sitting for just a few hours. Though the pain is mild it causes discomfort which starts a few minutes after i sit. I am just 17 years old and I am really worried. 2 months back i was travelling and was sitting in an auto in a very uncomfortable postion with a heavy bag on my lap. I sat just for half hour but i felt pain just after 5-10 minutes. It waas very strong pain and i believe that was the cause. After that day i have not been able to sit long hours