I wouldn't wait a year before getting a medical check up. I'd go right away so you can rule in or rule out a serious medical issue, or possibly just a medical issue that has a reasonably easy solution that can help your overall health (not just your hair health).
A few other thoughts in the meantime: noticed you didn't mention using a sulfate shampoo. What you describe sounds like it could easily be months of product build up that can only be remedied with the use of a good old fashioned sulfate shampoo (a clarifier). And since your hair still absorbs water easily, another possibility is hygral fatigue (too much moisture), in which case you might try wetting your hair much less frequently (including less frequent shampoo). Also, take inventory of any thermal or chemical treatments you've used on your hair. Cut those things out, or if you blow dry, do it w/a diffuser on the "warm" setting only.
Another thing is to assess how much fluid you are consuming daily. If needed, drink more water. Hydration of hair (and other appendages of the skin) happens from the inside out, not just from conditioning treatments. Also, if you live in a dry climate, try avoiding hair products w/humectants (like things w/glycerin or honey).