getDatabase called recursively sqlite insert and getReadableDatabase()

I just started with my first App and I am trying to create a table settings, which should contain an entry PIN. after that I want to run the method getPIN() to get the value of this setting.

The problem is, that I get always the error "getDatabase called recursively". As I just started with this, I have no idea how to fix it. I've seen a lot of used to have the same problem, but the solutions doesn't work for me. Could you please help me to understand what I'm doing wrong.

The contacts table was part of a tutorial I followed before, that´s the reason it's still in there.

Thank you.

This is my Database Helper

public class DatabaseHelper extends SQLiteOpenHelper {

private static final int DATABASE_VERSION =3;
private static final String DATABASE_NAME = "contacts.db";
private static final String TABLE_NAME = " contacts";
private static final String COLUMN_ID = "id";
private static final String COLUMN_NAME = "name";
private static final String COLUMN_EMAIL = "email";
private static final String COLUMN_PASS = "pass";
SQLiteDatabase db;
private static final String TABLE_CREATE = "create table contacts (id integer primary key not null ," +
        "name text not null, email text not null, pass text not null);";
private static final String TABLE_SETTINGS = "create table settings (id integer primary key not null ," +
        "setting text not null, value integer not null);";





public DatabaseHelper(Context context){
    super(context, DATABASE_NAME, null,DATABASE_VERSION );
}
@Override
public void onCreate(SQLiteDatabase db){
    String ssetting = "PIN";
    db.execSQL(TABLE_CREATE);
    db.execSQL(TABLE_SETTINGS);

    db=this.getWritableDatabase();
    ContentValues values = new ContentValues();
    String query = "Select * from settings";
    Cursor cursor = db.rawQuery(query, null);
    int count = cursor.getCount();

    values.put("id",count);
    values.put("setting", ssetting);
    values.put("value", 0);

    db.insert("settings", null, values);
    db.close();

    this.db=db;
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion){
    String query = "DROP TABLE IF EXISTS"+TABLE_NAME;
    db.execSQL(query);
    this.onCreate(db);
}
public int insertContact(Contact c){
    db=this.getWritableDatabase();
    ContentValues values = new ContentValues();
    String query = "Select * from contacts";
    Cursor cursor = db.rawQuery(query, null);
    int count = cursor.getCount();

    values.put(COLUMN_ID,count);
    values.put(COLUMN_NAME, c.getName());
    values.put(COLUMN_EMAIL, c.getEmail());
    values.put(COLUMN_PASS, c.getPass());

    db.insert(TABLE_NAME, null, values);
    db.close();
    return 0;
}
public String searchPass(String uname)
{
    db = this.getReadableDatabase();
    String query = "select name, pass from "+TABLE_NAME;
    Cursor cursor = db.rawQuery(query, null);
    String a,b;
    b="not found";
    if (cursor.moveToFirst()){
        do {
            a = cursor.getString(0);
            b = cursor.getString(1);

            if (a.equals(uname)) {
                b = cursor.getString(1);
                break;
            }
        }
        while(cursor.moveToNext());
    }
    db.close();
    return b;
}
public int getPIN()
{
    db = this.getReadableDatabase();
    int pin=1;
    String query = "select id, setting, value from settings where setting='PIN'";
    Cursor cursor = db.rawQuery(query, null);

    if (cursor.moveToFirst()){
        do {
            pin = cursor.getInt(2);
            break;
        }
        while(cursor.moveToNext());
    }
    db.close();
    return pin;
}

}

and the MainActivity

public class MainActivity extends AppCompatActivity {
DatabaseHelper helper = new DatabaseHelper(this);
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    int pin = helper.getPIN();
    if (pin==0){
        Intent i = new Intent(MainActivity.this, Loginpin.class);
        startActivity(i);
    }
    if (pin==1) {
        Intent i = new Intent(MainActivity.this, Setuppin.class);
        startActivity(i);
    }
    //pin = helper.getPIN();
}
public void b_newOnClick(View v) {
    if (v.getId() == R.id.blogin)
    {
        EditText user = (EditText) findViewById(R.id.tfuser);
        String su = user.getText().toString();
        EditText pass = (EditText) findViewById(R.id.tf_pw);
        String spass = pass.getText().toString();

        String password = helper.searchPass(spass);
        if(spass.equals(password))
        {
            Intent i = new Intent(MainActivity.this, Welcome.class);
            i.putExtra("username", su);
            startActivity(i);
        }
        else{
        Toast.makeText(MainActivity.this, "Password incorrect", Toast.LENGTH_LONG).show();
    }
    }


}
public void onSignClick(View v) {
    if (v.getId() == R.id.bsign) {
        Intent i = new Intent(MainActivity.this, SignUp.class);
        startActivity(i);

    }
}

}

Thank you so much.

regards, S Kilimanscharo