Could vit.d3 cause horrible pain in the legs.i have it 6 and i was unable to walk on my left leg because of the pain below &above knee?

Unlikely, but: It does depend on the vitamin d levels, which probably are fine up to 50-60, hydroxy-vit-d-3, but if much higher may be some degree of risk. Some docs are concerned about kidney stones, and renal problems, and there is some concern regarding adverse bone issues at very high levels. However, the leg pain may well be secondary to alternative etiologies, so have a thorough exam and get diagnosed.