Hi and welcome,
Sorry, I can't help with DR's because i live in Australia, and as for talking sense into anyone, hmmmm that is often in the too hard basket :D But it may help if you had a better understanding, of why they don't think your situation is caused by MS. MS is suppose to be a clinical diagnosis, and to some respect a dx of exclusion, because the vast majority of sx's found in MS are not unique to MS but some sx's are more suggestive and others are red flags leading away from MS.
It's more typical for the brain and or spinal cord lesions that cause the sx's in MS, to 'not' effect all peripherals, or cause wide spread sx's through out the body, that pattern of sx's presentation are general red flags or in other words a strong indication of MS not being the most likely cause.
During the neurological appointments, the neurologist should of run through some basic tests [ http://www.neuroexam.com/neuroexam/content.php?p=2 ] and if any of those tests indicated abnormalities eg hyper-reflex, clonus, gait etc etc that is clinical evidence and depending on what those results are, it can indicate the more likely cause. You could also think of clinical evidence as being the hard proof, that something is physically wrong, which is more telling than anecdotal but as yet doesn't answer what is causing it.
The MRI has become an important tool in dxing neurological conditions, lesion type, size, location etc are all very important clues in determining what the condition could be. In MS there is the Mcdonald criteria for lesion location etc to aid in the diagnosis, subcortical is not one of the identified MS locations but subcortical lesions are associated with Migraine.
If over a period of 9 years, you still don't have any MRI lesions in other locations or clinical evidence that makes you more suggestive of MS, then the likelihood of MS is much lower on your list of possible causes, and if most of your sx's can and have beeen explained by your dx conditions. Then it would make sense to me, to actually be looking at non MS explanations, that could be inter-related or secondary issues associated to those dx conditions eg sleep apnoea, medication, incorrect pain treatment, physical conditioning etc.
Please make an appointment and speak to your primary doctor about what can be done to improve your life, be it medication changes, physcal therapy, hydrotherapy, counselling or what ever but please speak up and ask for help!