What Causes Electric Shock In Thigh While Walking?

Hi, My name is Rahat/F/25 yrs. My weight is 45kg and ht. is 5'' feet. From few days back i am feeling some kind of electric shock in my left thigh while walking and i cant walk properly at that time. I have one more problem, i am feeling a severe pain in the lower feet in the middle of my feet. i cant walk properly, this pain continues, i dont know what to do.History: - I have a back ache problem from last 6 months. no other issues as such.