Spinal Stenosis Surgery (hemi laminectomy L2-5)

It's been 10 weeks since surgery (hemi laminectomy w bilateral decompression L2-5). Have Physical Therapy 2X/Week and do exercises and walking every day. Walking on treadmill is OK for 20-30 minutes, but when I stand (especially on hard surface) I get severe pain on right lower back, groin and leg after 5-10 min. I would expect to be much better by this point - anyone with experience here? Is this normal?