I Am Having Tightness, Cramps, Dull And Achy Throbbing Pain

I am having tightness, cramps, dull and achy throbbing pain in my legs when I am standing or walking. The more that I am standing, the more the tightness in my legs gets worse. When I am walking, I become dizzy and unsteady and the tightness in my legs gets worse. The tightness, cramps, dull and achy throbbing pain starts from above my knees and goes down to the lower part of my legs. What tests can be done to determine this problem? What doctor or specialist should I see regarding this problem? Please respond soon.