unable to make second table in onCreate() android

Question

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

    public class Databasehelper extends SQLiteOpenHelper {

    public static final String Dname="info.db";
    public static final String table_name="exp";
    public static final String col1="CATEGORY";
    public static final String col2="STATUS";
    public static final String col3="AMT";
    public static final String col4="DES";

    public static final String table2_name="past";
    public static final String col12="past_exp";


    public static final String CREATE_FIRST_TABLE =
            "CREATE TABLE " + table_name + " (" +
                    col1 + " varchar(25), " +
                    col2 + " varchar(10), " +
                    col3 + " float(5,3), " +
                    col4 + " varchar(255));";

    public static final String CREATE_SECOND_TABLE =
            "CREATE TABLE " + table2_name + " (" + 
                    col12 + " float(10,2) NOT NULL DEFAULT '0.0');";

    public Databasehelper(Context context) {
        super(context, Dname, null, 1);

    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        // TODO Auto-generated method stub
        db.execSQL(CREATE_FIRST_TABLE);
        db.execSQL(CREATE_SECOND_TABLE);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // TODO Auto-generated method stub

    db.execSQL("DROP TABLE IF EXISTS "+table_name);
    onCreate(db);

    db.execSQL("DROP TABLE IF EXISTS "+table2_name);
    onCreate(db);

    }

    public boolean insertData(String category,String status,double amt,
            String des) {
        SQLiteDatabase db=this.getWritableDatabase();
        ContentValues cv=new ContentValues();
        cv.put(col1, category);
        cv.put(col2, status);
        cv.put(col3, amt);
        cv.put(col4, des);

        long result=db.insert(table_name, null, cv);

        if (result==(-1)) {
            return false;
        } else {
            return true;
        }
    }

    public boolean insertData2(float exp) {
        SQLiteDatabase db=this.getWritableDatabase();
        ContentValues cv=new ContentValues();
        cv.put(col12, exp);

        long result=db.insert(table2_name, null, cv);

        if (result==(-1)) {
            return false;
        } else {
            return true;
        }
    }

    public Cursor getData() {
        SQLiteDatabase db=this.getWritableDatabase();
        Cursor c=db.rawQuery("select * from "+table_name, null);
        return c;           
    }

    public Cursor getData2() {
        SQLiteDatabase db=this.getWritableDatabase();
        Cursor c=db.rawQuery("select * from "+table2_name, null);
        return c;           
    }
}

I need to make two tables-exp and past. I have created the two tables using exec in the onCreate(Sqlitdatabase db) method, but the second table is not getting created and the app crashes. When is the onCreate called exactly? I have created 2 databasehelpers in 2 different classes and using them one after the other. This is my database helper class... How do i make 2 tables using the same onCreate method in the database helper class that is given above

Do we need 2 database helpers for creating 2 tables or 1 is sufficient? Please reply as soon as possible. How do i make 2 tables using the same onCreate method in the database helper class?

logcat error:

09-12 20:33:19.178: E/AndroidRuntime(21084): Caused by: android.database.sqlite.SQLiteException: no such table: past (code 1): , while compiling: select * from past
09-12 20:33:19.178: E/AndroidRuntime(21084):    at android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method)
09-12 20:33:19.178: E/AndroidRuntime(21084):    at android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:882)
09-12 20:33:19.178: E/AndroidRuntime(21084):    at android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:493)
09-12 20:33:19.178: E/AndroidRuntime(21084):    at android.database.sqlite.SQLiteSession.prepare(SQLiteSession.java:588)
09-12 20:33:19.178: E/AndroidRuntime(21084):    at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:58)
09-12 20:33:19.178: E/AndroidRuntime(21084):    at android.database.sqlite.SQLiteQuery.<init>(SQLiteQuery.java:37)
09-12 20:33:19.178: E/AndroidRuntime(21084):    at android.database.sqlite.SQLiteDirectCursorDriver.query(SQLiteDirectCursorDriver.java:44)
09-12 20:33:19.178: E/AndroidRuntime(21084):    at android.database.sqlite.SQLiteDatabase.rawQueryWithFactory(SQLiteDatabase.java:1314)
09-12 20:33:19.178: E/AndroidRuntime(21084):    at android.database.sqlite.SQLiteDatabase.rawQuery(SQLiteDatabase.java:1253)