spiritgurl, reading your profile it sounds like it was at least a year since this assault.
If you were attacked with a weapon, and sustained injuries that never healed, the doc may be able to see that.
If you were assaulted only with his penis, it's highly unlikely that you have sustained injuries that can be visible at this time.
Sorry, I see you are visiting an ob/gyn. Same rules apply.
A therapist is not allowed to divulge your private conversations. I am assuming you are not a minor. I am not sure what the law is concerning a minor. You can check this out easily.
They can't tell anyone right?
What do I do if they ask me? I haveN't told any one
It would depend, I think, on what constituted the rape. Rape always involves force (or fear of resistance), but does not necessarily involve physical harm, except as it could involve the hymen. Brutality or perverted practices would probably leave their marks.