Poor you, I really hope you can find some relief from the pain and discomfort. I agree with others you need to seek medical advice.
The pillow between/under the knees is excellent advice as it helps to keep your pelvis aligned rather than tilted.
I'm not sure about heat/warmth though. It does help the pain, but if it is a slipped or bulging disc pressing on the nerve then cold/ice will help to shrink it so it may slip back into place. I was told to avoid heat and use ice. Cold also reduces inflammation if that is present. You will get conflicting opinions, so do what a medical practitioner advises.
Regarding the distance healing, say yes please to AprilJo. It won't do you any harm, and may well give you some relief.
The only other thing I can suggest is that when you start walking again you have your backpack transported. You are already using trekking poles all the time? If not, then check the adjustment for height/length and use them constantly to take some of the strain.
I've had injections to combat my sciatica (but I can feel it now tweaking in my bottom as I sit quietly on the sofa!) and they've helped a lot. However I have found that carrying extra weight does not help, so I carry a daypack with 3-4lbs worth of 'stuff' in it, and send my main pack on ahead. It's not ideal, but it makes my back feel better. If you can plan to send it somewhere within your walking distance, then if you find you want to go further you can carry it for another few km without too much problem. But if you send it too far and then can't make it, or if you want to stop sooner because you are with some great people then it does become a problem. You do not have to stay where you send your pack, but you can't send it to municipal or donative albergues as they are not open in the mornings to accept it.
Anyway, I wish you the best, and as pain-free night as possible, and hope you can find some ease to continue your Camino.