It could be MS, chances are that if it’s both arms it’s not a muscular thing so possibly nerve related.
The thing about relapses is that we quite often only truly recognise them in retrospect. Because they come sneaking up on us, we’re not quite sure it’s an MSy thing and so we just end up living with whatever it is till it goes. And then we say ‘oh that must have been a relapse!’ (Some of us are a bit stupid like that!)
Of course if it’s an every night but not during the day thing, it could be about your sleeping position, pillow etc.
But if you’ve ruled out sleeping patterns / positions and muscular things, then ultimately you are probably left with an MS thing.
And I reckon it’s probably about time you stopped having to explain that you’ve been diagnosed, then another doctor wasn’t sure. It seems to me that you have MS and all you are waiting for is an NHS neurologist to say the words. (Bloody nuisance that you’re having to wait all this time for something that’s probably inevitable!)
What you could do is see your GP, explain what you’ve said here and ask for guidance in potentially neuropathic pain treatments. Your GP should be able to give you a prescription for Gabapentin say, which you could try out. I understand you would rather avoid drugs, but my rehab specialist neurologist reckons you can take Gabapentin as an on and off painkiller rather than having to take it all the time.
But if it is a nerve thing, then standard painkillers won’t help at all (ie paracetamol, ibuprofen, etc).