First of all go and see your GP before you start any exercises.
A few exercises recommended for low back pain are abdominal contractions/pelvic tilt.
Lie on your back with your knees bent and hands resting below your ribs. Try to tighten your abdominal muscles to squeeze your ribs down towards your back. Try to slightly tilt your pelvis and hold for the count of three (Be sure to not hold your breath).
Try to do some stretching exercises and strengthening exercises focusing on your back, stomach and leg muscles.