Diagnosis Questioned

My neurologist appointment Monday was crazy!! A while back I had an MRI from orthopedics. It was in question because they identified another lesion. Monday my neurologist finally reviewed everything and said that it wasn't a lesion. They are unsure what it is but needed to know ASAP. She said that if that was present in my very first MRIs and overlooked that there's a possibility that I don't have MS!?!? I was sent for another MRI today so they can do a comparison of my first with a current with contrast. I'm so... confused. I've already been through All the testing, poking, prodding, and scans for the last going 5 years to get where I am and now they are saying it's possible it's not MS. Now I'm just waiting to see what they find. I just don't even know how to feel about this. Especially since I've been going through all the treatments for MS and with all the signs and symptoms matching. I could understand it if this was maybe just year two because I do know a lot of things mimic MS but this far in. Thoughts?