f you, as you say, have XY chromosomes, five o'clock shadow, and the cock you were born with hanging down and see a woman looking back at you, then two very different things are true. One, your identity and psychology are tied up in identifying with what you think is a woman, which is fine. However, barring any surgeries, you also are capable of impregnating a woman to create a new human, you will on average grow larger muscles than the average woman, you will never breastfeed an infant with your body, and you will never get pregnant as you will not grow a uterus. That is biology.
That's not biology.
For a start, your entire body doesn't have to be strictly male or strictly female. One cause of infertility is that key parts of the reproductive system do not match the sex of the other parts. Women can have internal, non-functional testes instead of ovaries, for example. It's not hard to understand that if that is possible for reproductive organs, it can be possible for other organs, like the brain.
Some people don't have the same chromosomes in every part of their body. Some women have XY chromosomes, and they can even have children: https://ancillary-proxy.atarimworker.io?url=https%3A%2F%2Fpmc.ncbi.nlm.nih.gov%2Fa...
Human gender and sexual development are complex processes, with many variations and subtleties. Biologists tend to think in terms of sexual characteristics, not binary sex. The transgender population includes people with a whole variety of somewhat unusual variations, some not all that well understood, but none the less biological in nature.