onCreate() method of SQLiteHelper is never called

I'm creating a database in android using SQLite.

I wrote my code to create a table called products in onCreate() method.

Then when I call add() method to add some values into the table, I'm getting an error that there is no such table called products.

Here is my SQLiteHelper class :

public class MySQLiteHelper extends SQLiteOpenHelper {

    //variable declarations and some code
    ...

    @Override
    public void onCreate(SQLiteDatabase db) {

        // SQL statement to create a products table
        String CREATE_PRODUCTS_TABLE = "CREATE TABLE TABLE_NAME ( " +
                "id INTEGER PRIMARY KEY AUTOINCREMENT, " +
                "url TEXT, " +
                "title TEXT, " +
                "price INTEGER )";

        // create products table
        db.execSQL(CREATE_PRODUCTS_TABLE);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // Drop older table if existed
        db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);

        // Create tables again
        onCreate(db);
    }

    void add(String url, String title, String price) {
    //some code
    }

I read from a similar question that onCreate() is not a constructor and it is called only when database doesn't exist, but database doesn't exists in my case too, so why is it not called?

I also learnt that we need to call getWritableDatabase() or getReadableDatabase()

But I'm not sure where to make such a call in my code.

I tried to put the 'table creating code' which is in onCreate() in my add() method. For first run, I didn't get anything, but from the next time, I keep getting an error that 'a table already exists'.

Now, how can I ensure that table is created properly only once, before I call my add() method to insert some values. Any help please?