Unfortunately, not all health care professionals have had any experience with transgenders. I don't know if they receive training in school on the anatomical differences of surgically transitioned transgenders, and if they do, it is probably a very small amount. The same goes for those in the mental health profession.
Have you ever read the inserts on a medication you are going on? They list quite a few side effects that could occur. That doesn't mean that all of them will. Just because transgenders are supposed to act like a,b and c doesn't mean that they will. If a healthcare worker is going by the book, then chances are they will want to see all of the signs of a transgender rather than using their heads and realizing that only some of the signs will be present.
Two memorable incidents with health professionals come to mind when I was going through transition. The first was a gynecological surgeon who told me that he was doing the surgery only because the hospital was making him do it. He didn't "believe in treating mental illness with surgery". The second was a nurse who despite my telling her several times that my urethra did not pass through my penis and to just cath. me as if I were a female, kept trying to get a urinary catheter to go through the penis. At the time, the hookup was too dangerous. I practically had to cath myself.
If you take it personally, it can really get to you. In the cis world, not all guys are macho and not all women are girly. You shouldn't have to prove you are the gender your brain tells you that you are, but at this time, you do. People are not all one way or another. There are shades of gray in gender, and just because you don't play football or have an interest in car engines that doesn't make you any less a man.
sam1234