Re: Severe lower back pain
This could be many things, some are serious and need medical treatment. Others are minor and require no intervention. You could have anything from a muscle strain to a ruptured disc. Most back pain resolves in about ten days without medical treatment. If you continue to have pain after ten days, or if you have bowel or bladder problems, or shooting pain into the legs, seek medical attention. If your inability to walk is due to weakness in the legs (as opposed to stiffness/pain in the back), then also seek medical attention.
The most important at-home treatment right now is ICE. This will help to bring down any inflammation. No heat for at least 72 hours, but even longer is better. Fifteen minutes on, fifteen minutes off is okay for the first couple days, then fifteen minutes of ice per hour, making sure that you have something between the ice and your skin. And continue taking anti-inflammatories per the label's instructions.
Try to rest the back while not immobilizing it. So, you don't want to be on bed rest, but lay off the heavy duty exercise for a while. Walking is a good exercise, once you are up to it. I would avoid any heavy lifting for the next ten days.
You may want to avoid acting stretching for a few days. Instead, if your back tightens up, lie down and put your feet up to rest the back and allow the muscles to relax. It's okay to lie down and rest: when I say you don't want to be on bed rest, I mean that you should not have someone bringing you food and a bed pan!
I think that there is a post from a week or two ago titled "Initially" which has further good information on first aid/home care for back injuries.