Give me a few days to think about an appropriate response.
Few issues 1st,
1. How is your relationship with your father? Do you think this is something you would be able to talk to him about privately? Do you know your father loves you and would do anything for you? How is your family relationship?
The reason I state this is all parents generally walk through much of the same feelings their kids do when they were young. If you are able to share this with someone it may be better. You need to be able to determine this.
2. Make sure you give yourself a break from messing with it (at least 1 week plus).
3. I did some initial research. I believe your goal would to be referred to a urologist by your doctor. I don't know what you did, but a urologist has more training on what would cause problems of your erection and what solutions are available. At the age of 15, I do believe your parents would need to be aware if you see any doctor especially if they are paying the bill. With your primary care doctor, you may not need to go to specifics, but with a urologist, you would need to go to details. Please note to encourage you, whatever you did or done would probably not be new in the eyes of a urologist. They probably have seen it all. You will need to give them the information to help you.
Like I said, let me think about this a little more.
I hope otherwise you are doing well! Are you into football this weekend. I am an eagles fan and hope they finally get to the superbowl.
Do you do any exercise (weight lifting, running, swimming, anything) to reduce stress of being a teenager? Life will change to the better once you graduate from highschool/college.
Best wishes,
tom