Here's a great stretch for your back: lie down (on a yoga mat, clean carpeted place, etc.--not a bed, which is too squishy). Bend right knee up towards your chest, grab leg just below knee with both hands, and pull up as far as you can toward your shoulders. Keep it there for about a minute (longer time necessary for good stretch). Put that leg back down slowly, repeat with other leg, then both together. Repeat four or five times. You should feel this in your lower back as a good stretch. Then stand up, clasp hands as far above your head as possible, and stretch your side by bending as far as you can from left to right, then right to left. Hold stretch, then drop arms, rest a few seconds and repeat. Last, put hands on lower back and bend backwards as far as is comfortable. Hold stretch for 20 seconds or so, straighten up and repeat four or five times. Do these every hour or so, and walk around during this rest time.
These exercises were taught to me by my physical therapist and have really, really helped my bad back problem. Go for it!
Dana