I feel for you!
I still have sciatica which is worse if I do manage to sleep for a few hours (am a poor sleeper). In other words, if I have been still in one position, this is what sets me off, so can't win (sciatica or sleep!).
Twenty plus years ago my sciatica came on relatively quickly and soon I couldn't stand the nerve pain which pulsed every second, so had surgery (but even that took three weeks to arrange as all the surgeons were away on holiday - school holiday season!).
Then, relatively pain free it has returned on the other side but not nearly as badly (my spine is disintegrating and pressing on the spinal cord - with also a tumour - but that's another story). When I feel a twinge I immediately do the stretching exercises first given to me and they really do help.
Back to you: please speak to your doctor and see if he will prescribe Pregabalin or Amitriptyline. Both are for nerve pain and really can help.
Keep up gentle walking but I was advised to stop as soon as the pain worsened. Sit somewhere (a garden wall, for example) for five - 10 minutes, then carry on and repeat if necessary. My physiotherapist told me not to walk and 'push through' the pain, as this would only make things worse.
Try not to carry anything heavy as you could feel an immediate uptick of your pain. Make several journeys if necessary but don't carry heavy weights.
I hope your doctor can prescribe some pain relief for you and oh, if it is of any use, I was told that many sciatica problems are self-limiting but can take a few years to completely dissipate..... It depends how much pain is too much for you.
I wish you the very best and when fully recovered from your surgery, can take painkillers directed at nerve pain, do the exercises to keep moving and slowly, hopefully, you will recover.