Help with mystery pain.

Patient: My husband has very lower back ache/dull pain that radiates down to the top of the back of his thighs. No fever. It hurts more when he’s lying down. He has a slight pressure when urinating, but no pain in kidneys, bladder, or when urinating. Do you know what could be causing this?

Symptoms: Lower back pain and ache, slight pressure urinating. Pain down to top of back of thighs.