For past 3 days I have severe back pain. My spine doesn't hurt by back area above right hip hurts bad and the pain usually reaches till my right knee.?

Back pain. I would have you rest from physical activity. Use otc analgesics ie acteomeniphen, ibuprofen and apply ice off and on if there is back muscle spasm otherwise apply heat dry or wet to the painful area. If it is not getting better in three days then see your physician.
Sciatica. This pain you are describing can be due to a few different conditions. It can be referred from the back. It can be a pinched nerve in the back. It can be irritation of a tendon on the leg called the iliotibial band. It can even be due to the hip joint itself.
SEE A PAIN DOC. As mentioned by other physician postings, it could be a number of issues. The sooner you see a board certified pain physician, the sooner you will have a diagnosis, get the proper treatment, feel better, improve function and quality of life. Why suffer? It may go away on it's own. A doctor will just help you feel better faster.