You may have something called neurogenic claudication. This is usually caused by spinal stenosis. Usually the symptoms include numbness/tingling, pain, weakness in the lower extremities when walking over a certain distance.
In this disorder, the patient usually has to sit down or bend over for the symptoms to go away. This is in contrast to vascular claudication, which is pain in the legs due to poor circulation, where patients usually only have to stop walking, but not sit down.
If the symptoms continue or get worse you should see your physician for an evaluation. Good luck.