severe shocking lower left back/butt pain? Pulled muscle?

I have been having severe shocking lower left back/butt pain for 4 days. The pain extends down the left leg but only as a throbbing ache. I have not injured it to my knowledge. I did reach to pick up something when I first felt the pain. I have trouble rising from sitting, if I dont walk slow I get a shock of pain that hurts so bad I gasp. It hurts when I do anything just about. I does not get better if I rest. It gets terribly worse if I stand for any length anf try to walk. I just am wondering if this is just a pulled muscle or if I should see a doctor. I dont want to go if it is something that will heal on its own. TIA