Since you are feeling bad about being dropped as a patient I suggest that rather than speculate that you call the doctor's office and ask? Some doctors take missed appointments very seriously, especially if they have a busy practice and you didn't notify them in advance. This happened to my daughter some years back. If you suspect it is because you are turning 65 you could call and simply ask if this doctor accepts Medicare patients. If the response is "no" you have your answer.
My male internist is absolutely the best. Wish you luck on finding a new doc who meets your needs.