A mom of someone with cystic fibrosis traced her child's lung bleeds to exposure to chemicals used in a dark room to develop photographs. They were then able to prevent further bleeds, at least from that source. (IIRC, her child was a teen or young adult taking a class or pursuing a hobby.)
A woman who works at the CDC was undergoing cancer treatment. Her husband took photographs regularly of her arms, I think. Photographic evidence convinced them her symptoms were getting clearly worse. They used this to convince her doctor to change her chemo drug sooner rather than later.
My primary care doc took a big interest in seeing my daily numbers when I mentioned that I'd (systematically) tracked a recent change to my health into a table of readings. If you create a graphical plot of a relevant metric, I bet that'd be of even greater interest to any competent health professional.
IMO, if your doc isn't interested in such data, get another doc.