I am sorry to hear that you are experiencing such discomfort. As this has been going on for quite a while, I definitely suggest getting in to see your primary care doctor
so that a diagnosis can be made and treatment started if necessary.
It is likely that all of the cramping and numbness
that you are experiencing is simply due to the fatigue of your job, which involves standing on your feet for prolonged periods of time. Make sure that you always wear supportive shoes could help, as could engaging in an exercise program to strength the various muscle groups in your legs and feet.
Another possibility is plantar fasciitis, which is an inflammation of the tissue on the bottom of your foot probably from standing. Your doctor could diagnose this and prescribe some simple stretches to help.
Although it is very unlikely, it is possible that this is a problem due to smoking. Smoking causes damage to the blood vessels and, over time, can lead to narrowing of the vessels, which can cause cramping and numbness in the legs, known as claudication. Stopping smoking would be good for your health regardless, as you known.
See your primary care doctor as soon as possible.