I have a 'thing' for my doctor.
What are you saying?
I fantasize them in stockings.
It's normal to find certain people attractive, but you shouldn't be fanaticizing about your doctor. If the attraction you feel toward your doctor is that strong you should start looking for a new doctor.
I'm trying to seduce her.
Well she might be attractive but you should not try to seduce her. This is her job and she needs to abide by the ethics, seeing a patient romantically can get her fired. I'd suggest you transfer to a different doctor.