I've had pain radiating my lower buttocks down through my lower leg as well as veinsin the back of my knee. Family is conccerned its a blood clot?

Sciatica or Clot. Blood clots cause pain and swelling in the foot, lower leg, and seldom move up the leg to the buttocks. Irritation of the sciatic nerves usually started in the lower back to buttocks area with pain going down the back of the leg. Pressure in the back of the knee on the nerve could cause pain up to the buttocks and down to the foot. Check with your physician immediately for testing and treatment.
Radicular pain. Pain that radiates from the buttocks or back, and travel down the leg is known as radicular pain. This is usually due to nerve impingement to the lower back (aka sciatic pain). The most common and prevalent symptom of a clot is swelling to the foot, ankle, and lower leg. Best to see your family doctor or internist to find out your cause of pain.