diagnosis

As long as you are not deemed a danger to yourself or someone else, you are protected by doctor/patient confidentiality.

Go speak to a doctor and get the help that you need. Do not hesitate. It is not too late to take control of your life from any condition you may have.

Thank you for answering. Does the doctor have the right to spea to my mother if I tell him that I self-harm and have suicidal thoughts? The problem is that I'm so afraid of many thing and if the worst would happen like he'd send me to a psychiatry, I'd die, I don't want to go there

You can ask the doctor directly what the laws and rules are for you specifically, so you go in knowing ahead of time what the consequences of talking about your problems will be. I'm pretty sure that if you are under age then your parents have a right to ask what was discussed during your sessions or to see your medical records.
However,there are laws regarding putting someone in an institution or requiring them to seek treatment, the law for that states that you can't make someone do it against their own free will. You should seek help when you feel you need it, because it is for your own benefit to do so.