Android database SQLite doesn't work

I need help. I'm trying to create a new sqlite database on android (my app has just one which works fine) but when I create the second, the activity goes in crash.

This is my code. Could you give me an hand?

Following the second activity (doesnt't work)

 com.example.memopad;

import java.util.ArrayList;
import java.util.Calendar;

import android.annotation.SuppressLint;
import android.app.DatePickerDialog.OnDateSetListener;
//import android.app.DialogFragment;
import android.app.PendingIntent;
import android.content.ContentValues;
import android.content.Intent;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.support.v4.app.FragmentActivity;
import android.support.v7.app.ActionBar;
import android.support.v7.app.ActionBarActivity;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.AdapterView;
import android.widget.AdapterView.OnItemSelectedListener;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.DatePicker;
import android.widget.EditText;
import android.widget.Spinner;
import android.widget.TextView;
import android.widget.Toast;
import android.support.v4.app.Fragment;
import android.support.v4.app.DialogFragment;
import android.support.v4.app.FragmentManager;

public class Birthday extends ActionBarActivity 
{

    private PendingIntent pendingIntent;
    private EditText inserisciNome;
    private TextView impostaData;
    private Button BackButton2; 
    private Button AggiungiData;
    private EditText inseriscigiorno;
    private EditText inseriscimese;
    private EditText inseriscianno;
    private int year;
    private int month;
    private int day;
    private Spinner spinner1, spinner2;
    private ArrayAdapter<CharSequence> adapterG ;
    ArrayAdapter<CharSequence> adapterM;
    AdapterView<?> parent;
    int pos;
    String giorno;
    private HelperB helper;
    private SQLiteDatabase dbwrite;
    private SQLiteDatabase dbleggo;
    private ArrayList<String> archivioNomi;
    private ArrayList<String> archivioGiorni;
    private ArrayList<String> archivioMesi;
    private ArrayList<Long> listaId2; 







    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.birthdaylayout);

        recuperaView();
        setAllListener();
        SetAdapterSpinner();
        //inizializzaDb();


        //addListenerOnButton();




        Intent alarmIntent = new Intent ( Birthday.this,AlarmReceiver.class);
        pendingIntent = PendingIntent.getBroadcast(Birthday.this, 0, alarmIntent, 0);






}       

        public void recuperaView(){

        BackButton2 =(Button)findViewById(R.id.returnback2);
        AggiungiData=(Button)findViewById(R.id.aggiungiBirth2);
        inserisciNome=(EditText)findViewById(R.id.mioEditText);
        spinner1 = (Spinner) findViewById(R.id.spinnerDay);
        spinner2 = (Spinner) findViewById(R.id.spinnerMese);





}
        public void setAllListener(){

            AggiungiData.setOnClickListener(new OnClickListener() {

                @Override
                public void onClick(View v) {


                inserisciinDB();


                Toast.makeText(getApplicationContext(), inserisciNome.getText().toString() + " " + spinner1.getSelectedItem() + " "+ spinner2.getSelectedItem() ,
                        Toast.LENGTH_SHORT).show();





                }
            });
            BackButton2.setOnClickListener(new OnClickListener() {

                @Override
                public void onClick(View v) {
                    Intent i = new Intent ( Birthday.this,MenuActivity.class);
                    startActivity(i);

                }
            });




        }   
            private void inizializzaDb() {
            helper = new HelperB(this);
            dbwrite = helper.getWritableDatabase();// rendo scrivibile il db
            dbleggo = helper.getReadableDatabase();// db diventa leggibile
        }   

            public void inserisciinDB(){

                ContentValues dati = new ContentValues();
                dati.put("nome", inserisciNome.getText().toString());
                dati.put("giorno",spinner1.getSelectedItem().toString());
                dati.put("mese", spinner2.getSelectedItem().toString());
                dbwrite.insert("birth", null, dati);
                aggiornaElenco();
            }

            public void aggiornaElenco(){
                final String sql2 = "SELECT * FROM birth ";
                Cursor cursore = dbleggo.rawQuery(sql2, null);
                archivioNomi=new ArrayList<String>();
                archivioMesi=new ArrayList<String>();
                archivioGiorni=new ArrayList<String>();
                listaId2=new ArrayList<Long>();
                while (cursore.moveToNext());

                    listaId2.add(cursore.getLong(0));
                    archivioNomi.add(cursore.getString(1));
                    archivioGiorni.add(cursore.getString(2));
                    archivioMesi.add(cursore.getString(3));
                    //System.out.println(cursore.getLong(0));






            }


            public void SetAdapterSpinner(){

                adapterG = ArrayAdapter.createFromResource(this,
                    R.array.giorni, android.R.layout.simple_spinner_item);
                adapterM = ArrayAdapter.createFromResource(this,
                    R.array.mesi, android.R.layout.simple_spinner_item);
                adapterG .setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
                adapterM .setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
                spinner1.setAdapter(adapterG);
                spinner2.setAdapter(adapterM);
            }

            public void onItemSelected(AdapterView<?> parent, View view, 
                    int pos, long id) {



            }

            public void onNothingSelected(AdapterView<?> parent) {
                            }


}` 

this is the helper class`age com.example.memopad;

    import android.content.Context;
    import android.database.sqlite.SQLiteOpenHelper;
    import android.database.sqlite.SQLiteDatabase;

    public class HelperB extends SQLiteOpenHelper {
        private static final String DB_NAME="_db";
        private static final int DB_VERSION=1;
        public HelperB( Context context){
            super(context,DB_NAME,null,DB_VERSION);
        }

     public void onCreate(SQLiteDatabase db2){
         String sql2="";
         sql2 +="CREATE TABLE  birth(";
         sql2 +=" _id INTEGER PRIMARY KEY,";
         sql2 +=" nome TEXT NOT NULL";
         sql2 +="giorno TEXT NOT NULL";
         sql2 +="mese TEXT NOT NULL";
         sql2 +=")";
         db2.execSQL(sql2);

     }
     public void onUpgrade(SQLiteDatabase db,int oldVersion,int newVersion){}
    }`