Winston doesn't sell bikes or bike parts, he sells a proper bike fit. He wouldn't be as successful as he is if he simply changed your fit to sell you something else. Most bike fit professionals are the same.
Also, it's funny you always hear people talk about not needing a professional fitting, its a waste of time, wast of money, etc., but I can't recall anyone who's actually done it say such things. Quite the opposite.
Much of what you say points exactly to someone who could benefit from a proper fitting. You have had injuries in the past, you have one leg which is longer than the other, you recently started riding longer distances more frequently/ regularly and now are starting to feel pain, you are sensitive to seemingly small changes in seat height, you are getting older.
I don't know why getting the advice you asked for is scary and unmovtivating, but I'm in the same camp as the others. Seem to be a candidate for a proper fitting and the suggestion of a scan to confirm its just tendonitis, not more serious structual damage, is a good one.
Good luck, I hope you get the problem settled.