Good questions that show a lot of maturity for a 16 year old. Your doctor is required to turn you in to the authorities if you tell him certain things where he feels you are at imminent risk of harm.
You could be deemed emancipated at 16 depending on certain factors. Thus, if the law sees you as no longer a minor, at 16, then you do not have to fear what you tell your doctor. Having intimate relations with a person who is 5 years older than you cold be legal statutory rape if it is determined that you are still a minor. Minors cannot legally give their "consent" to having intimate relations. It is not legally possible for a minor to say "yes". He could be charged with felony rape. You may be making some of the worst decisions of your life. Good luck.