After Sitting On Toilet For Approximately 5 Minutes My Left

After sitting on toilet for approximately 5 minutes my left leg goes completely numb from my waist down to my toes!! It takes me quite a few minutes to regain feeling and able to walk again!! I've recently seen my PCM regarding left lumbar pain in left back,hip and occasionally groin area!! She has referred me for PT bcoz she thinks I have a tight muscle,but I honestly believe I have a sciatic nerve issue or sacroiliac issue!! What do you think?