Writing your own nexus letter?

Has anyone wrote their own nexus and does it work? Vetclaims.ai has a template for migraines secondary to tinnitus. I have SC for tinnitus already, a years worth of migraine buddy tracking, including printouts from our HR system showing the days I called off work because of having to lie down in a dark room, as well as a script for sumatriptan. Is that enough to file a claim or do i need a docs nexus? I'm guessing it would be enough to get a C&P but the doc I'm seeing doesn't do nexus letters.