Mussel ficilitations and cramps in legs !

Hi, after 6 months of facilitations in legs and cramping on walking more than 1 mile, at only 56 years of age and an M.R.I. scan, showing nothing neurologically and blood lactate tests.I am taking .5mg of Clonazepam about three times per day .
The lactate tests showed no change as each sample was taken during a controlled exercise test. I think they should have showen an increase in lactate on exercise and a drop off on rest? Does this indicate a possible metabolic problem? What organ controlls Lactic acid supply to the mussels ? Could it be diet ? Like too much milk causing to much Lactate.
Any Ideas ? Thank you ,
                        Grant Hudson
                          Landscape Artist, NewZealand.