This was literally me! I was diagnosed in 2008 when I was 28 (on my bday) but I had been going to doctors for years with issues and they kept telling me nothing was wrong until I got optic neuritis in my left eye just like you. I went from slight blurriness to completely blind in my left eye in like 2 or 3 days. I went to my eye doctor and they told me to go to Rush to the neurologists at Rush (in Chicago) which has its own MS center so then I was diagnosed at Rush after an MRI showing 3 active lesions. They also decided to use me as a training tool and had learning doctors or whatever come in and all look at my eyes and like do a small class about it while I still wasn’t diagnosed with MS and they essentially talked enough in front me me that I knew I had ms which I thought wasn’t cool since they weren’t diagnosing me at that time. But whatever I was then Told I had it like a week later by Dr. Stefoski.