I have constant pain in my lower back, legs and feet and feel tired all the time what can it be?

Look at lumbar spine: The first concern is your physical condition. Are you slim and physically fit or heavy and out of shape? If there are no obvious causes, get a MRI scan of your lumbar spine. The fatigue is of concern. If you are heavy and smoke, solution may be straightforward - lose weight, stop smoking, start exercising. Do you have diabetes? If not, get some blood tests to check for it.