*BIG BIG HUGS* to you
Is this a regular doctor (physician) you're going to? If so, what happens will vary. They may or may not say anything, though they probably will. The doctor may refer you to a therapist.
If it is a psychiatrist (a mental health doctor), then that's a different story. He or she will likely ask you a bunch of questions- alone, and with your mom in the room, and then he or she will probably want to talk to your mom alone.