So at first I thought you meant something else, but what I misunderstood is still really interesting.
An app where you can just list your symptoms and how they change over time and then gives you a percentage chance that you may have any given condition. Kinda like… “My back hurts, it’s been hurting for a week and getting worse, my skin feels dry, had a headache three days ago…” and the app tells you you might have some this-or-that infection.
I don’t know how doable this is at all.
Sorry but I don’t know about your particular issue… I would recommend just using Sheets? I mean, based on what you’re saying you just want something where you can easily input a number (pain level) or symbol (took meds/didn’t take meds) over time on a few different axis and get a visual representation (graph). Why not just use Sheets?
doesn’t sound good