After walking about a mile, i get a weakness in my right leg with a pinching feeling in a vein behind my knee. it makes me drag my leg. what is it?

Consider disc diseas: You're a little young for a slipped disc in your back, but it's possible. Any loss of sensation in the leg? Any weaknes in the leg. Mri might be needed. See an orthopedist or neurosurgeon.

Claudication: This sounds like claudication which is a clinical diagnosis given for muscle pain (ache, cramp, numbness or sense of fatigue), classically in the calf muscle, which occurs during exercise, such as walking, and is relieved by a short period of rest. It is most commonly due to peripheral arterial disease or lumbar spinal stenosis. See your family doctor to sort this out.