Good evening Dr Su,
Thank you for your question.
The most common nerve affected in the lower back is the sciatic nerve which passes through the sciatic notch in the buttock, predominantly to the posterior or lateral thigh, calf and lasteral foot, or great toe.
Less commonly, the Femoral nerve passes from the upper lumbar spine, through the pelvis and exits via the groin to the anterior thigh, exactly in the pattern you describe.
The stretch test for the Femoral nerve is more difficult than that for the Sciatic nerve which can easily be done at home (Slump Test). It needs to be done by a competent and experienced clinician.
Do you get pain on forward bending, or extension and/or lateral flexion?
A short leg is always a factor in leg pain, but more so in lesions of the Femoral nerve. Have someone examine you for a leg length inequality.
I recommend you start immediately with the lower back exercises described at Chiropractic Help, using your discretion and common sense. The goal isn't the London summer Olympics! Before you get out of bed in the morning is best.
It's best to take leg pain seriously. See someone...
Dr. Barrie Lewis