Go to a doctors or sexual health clinic about it, if you don't want to alone just tell someone I think I have bacterial vaginosis and they can take you to the doctors, confirm it and get you antibiotics
At 15, you have said your self harm has allowed many men to take advantage of you.
There are many myths surrounding self harm and reasons behind it. For sure, it is becoming more common for young people now.
If you ever need to talk, I recommend seeking professional help, available through your GP.
They are used to such questions and can guide you into path of recovery.
If not, at least pick up the phone anonymously and talk to someone qualified to listen to those with personal trauma and family rejection.
But, the first step must start with you. Stay safe.