Not being active can reduce your body's use of nutrients and if you haven't been eating right that can also contribute.

Numbness is a nervous-system thing that's usually caused by diabetes, poor circulation, or both.

If you feel light-headed after activity it could be an iron deficiency. If you really want to know, head to a physician and ask to have a complete blood work-up done to know how your blood's chemistry is. That will tell you just about everything you need to know.