Welcome to Healing Well A negative spinal tap doesnt necessarily mean you don't have MS, but there are certain criteria that need to be met before a diagnosis can be made. Here's an article with the criteria that might explain things a bit better for you.
It is good that you are seeking out other possibilities, there really are so many illnesses that can mimic MS and sometimes it can take a while to figure it all out so try to hang in there. Fibromyalgia and diabetes are some other conditions you could check out too. I do hope you start to feel better soon, let us know how things go.