Thank you for reaching out to us.
When a female doctor of a comparable or higher level of expertise is readily available, one should choose her over a male doctor.
In your case, where seeing a specialist could be important, but all the finiancially accessible specialists are male, it is fully permissible for you to see one of them.
As long as the door to the exam room is not locked and there is a possibility that another professional at the office could enter, there is no concern of yichud (a man and woman being secluded together). You should dress in a way that will enable you only to expose what is necessary for an exam.
Refuah sheleimah! Please let us know if we can be of further assistance.