Android sqlite insert error. return -1

I wrote the following code but some reason insert function does not work. I tryed remove the database and the tables but nothung work!!

    @Override
public void onCreate(SQLiteDatabase db) {
    db.execSQL("CREATE TABLE " + steps_table +  " ( "+id_col+" INTEGER PRIMARY KEY AUTOINCREMENT, "
    +steps_number_col+" INTEGER, " + date_col+" TEXT) ");
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
    db.execSQL("DROP TABLE IF EXISTS " + steps_table);
    onCreate(db);
}

public boolean addStep(Step step)
{
    SQLiteDatabase db = this.getWritableDatabase();
    db.execSQL("CREATE TABLE " + steps_table +  " ( "+id_col+" INTEGER PRIMARY KEY AUTOINCREMENT, "
            +steps_number_col+" INTEGER, " + date_col+" TEXT) ");
    ContentValues contentValues = new ContentValues();
    contentValues.put(steps_number_col, step.stepNumber);
    contentValues.put(date_col, "dfg");//new SimpleDateFormat().format(step.date));
    if (db.insert(steps_table, null, contentValues) != -1)
        return true;
    return false;
}