I know it's difficult but please ask them to do a MRI of your brain. Sometimes Dr's don't want to be the bad guy.
Having a primary relative (full sibling or parent or child) with MS only increases the risk of developing MS by about 5% as compared to the rest of the population.
A positive EMG actually points away from MS as a cause of neuropathy as it only accounts for disordered signals in the peripheral nervous system. MS is a disease of the central nervous system. Nothing you've mentioned sounds particularly indicative of a potential neurological condition.
Your sister is currently going through what is a very difficult time for most of us - that first year post diagnosis. It's a time that can be fraught with hyper-vigilance, concern for family, and adjusting psychologically and physically to having a chronic condition.
However, as I'm sure you know, there is no one single test that diagnoses MS with 100% specificity. It's the overall picture based on neurological exams, imaging, patient history, and ruling out other more likely causes. I think it might be a very stressful and unsatisfying endeavour to be thinking about MS testing for yourself at present. It just doesn't fit what you've described.
You have been dealing with a few things that have been diagnosed that could already account for your symptoms. I would speak to your GP about getting adequate symptomatic relief and treatment for your current diagnoses.