Really sorry to hear you are having to cope with this on top of the diabetes

I know how horrible neuralgia is - I get bouts of it from time to time, though thankfully only brief ones.
I don't know very much about MS treatment, so can't help on the meds front, if it does turn out to be that, but I do know that as far as symptoms are concerned, MS is very similar to ME (in fact, I know a couple of people who have been back and forth between specialists for a while being told "you have ME" ... "no, you have MS" ... "no, you have ME" ... and so on. Brain scan abnormalities, walking difficulties to the point of collapse or being unable to get up at all, pain (usually in muscles but also including neuralgia), finding it hard to relax, and feeling twice your age are all normal in ME as well as in MS, so if you want info about any of these or other overlapping symptoms feel free to pm me.
Numbness isn't usually a symptom of ME, however, and I don't think the brain abnormalities it causes would be described as lesions, so I don't
think whatever you have is likely to be ME, however ...
the more exercise I try and do to get fitter, the worse it is on my muscles.
... this really rang alarm bells for me - the primary diagnostic criteria for ME is "post-exertional neuro-immune exhaustion" - in other words any exercise makes you ill. I don't think it's quite the same with MS, but I do know that people with MS become exhausted after a small amount of exercise, and have to pace themselves. In both cases the advice is always to pace and never to push yourself, so exercise should be gentle and/or brief, always stopping
before you start to hurt or get tired. So if your exercise is hurting you, I'd change what you do or cut back on it, if I were you, at least until you know what's wrong, as it could be making you worse. I know that's not ideal with diabetes, but it's better to be doing something gentle now and something gentle in a few years' time than to be doing something strenuous now and as a result being unable to do anything at all in a few years' time. There's more about exercise on the MS Trust site here:
https://www.mstrust.org.uk/a-z/exercise (though bear in mind that if it is not MS you have, this might not be the right advice - it certainly wouldn't be for ME).
I hope you are able to get a diagnosis soon and don't end up being sent round from pillar to post. At the very least I hope you are able to get some pain relief - ask for a referral to a pain specialist if you haven't already had one. If you are the sort of person who finds it helpful to know about symptoms and diagnostic criteria there's info. about MS here:
https://www.mssociety.org.uk/what-is-ms/signs-and-symptoms and here:
https://www.mstrust.org.uk/a-z/diagnosis (and if you want to compare, the diagnostic criteria for ME are here:
http://www.meassociation.org.uk/wp-content/uploads/2011/07/ICC-short-version.pdf ).