OUCH!
That sounds really nasty Lynn.

I do know that sleeping on a heating pad, or leaving it on for extended periods of time can make things worse. Putting it on for 20 minutes at a time and then leaving it off for at least 30 minutes before re-applying it is the better way to go.

Leaving a heating pad on for longer than 20 minutes can cause the blood vessels in the area to stay dilated, which allows de-oxygenated blood to settle in the area. That can cause more inflammation and pain.
The alternative is to use a non-electric heat source that will naturally cool down after application. That way you can fall asleep without having to worry about taking it off.

The scan results of your spine might indicate that you have a partial transverse myelitis going on, so maybe ask your neuro about that. Partial TM can certainly cause the sort of pain and spasm that you have been having; but so can facet joint degeneration. There is a treatment for the facet joints where injections are put right into the joints and that helps a lot of folks. You might ask about that too.

I hope you get some answers and relief too. Having to work longer hours while you are going through this is a tough row to hoe. is there any chance of you getting some time off?

With love, Erika