it is striking how many people want to say it's not race (or being a doctor!).....
I have no doubt a significant proportion of white men would either rule out dating a black woman, hesitate more, and/ or come into chats with preconceptions that were a barrier. While sad, it's reality- and it is not just extreme racists who would blurt out aggressive, recognizably racist shit. It's people who may not even be aware they are doing it and would never consider themselves racist. (I think this is true of many people from many different ethnicities looking for a partner).
Similarly, being a doctor as a woman WILL put off a number of men.....
Any man who is put off by either of these things is clearly not someone you can find happiness with OP.... so I can only suggest you keep looking and I am sure the right guy, with none of these issues, will be waiting somewhere.
There may also be all kinds of other reasons why it's not working yet......But let's not try to comfort ourselves that the whole of the male species is free of prejudice and sexism?
I am sorry that OLD - which is really tough for everybody- May be even tougher for you, for totally unfair reasons, OP. I wish you luck, though and you sound lovely so am sure you will find happiness with someone who deserves you!