Android Studio|| SQLite Error when create multiple table

Question

I try to create multiple table in one database by using SQLiteOpenHelper. This is code for create table:

public void onCreate(SQLiteDatabase db) {
    /**Create table for user account*/
    String CREATE_TABLE_USER = String.format("CREATE TABLE %s " +
                    "(%s INTEGER PRIMARY KEY AUTOINCREMENT, %s TEXT, %s TEXT)" ,
            User.TABLE,
            User.Column.ID,
            User.Column.USERNAME,
            User.Column.PASSWORD
    );/**Create table for add subjects*/


    String CREATE_SUBJECT_TABLE = String.format("CREATE TABLE "+Subjects.TABLE_S+" ("+
            Subjects.Column.ID+" INTEGER PRIMARY KEY AUTOINCREMENT, "+
            Subjects.Column.USERNAME+" TEXT, "+Subjects.Column.SubName+" TEXT)");

    db.execSQL(CREATE_SUBJECT_TABLE);
    db.execSQL(CREATE_TABLE_USER);
    db.execSQL("PRAGMA foreign_keys = ON;");

    Log.i(TAG, CREATE_TABLE_USER);
    Log.d("CREATE TABLE SUCCESSFUL",CREATE_SUBJECT_TABLE);
}

And this is code for add subject to table subject:

public long addSubject(Subjects subjects) {
    mDatabase = this.getWritableDatabase();
    ContentValues values = new ContentValues();
    values.put(Subjects.Column.USERNAME,subjects.getUsername());
    values.put(Subjects.Column.SubName,subjects.getSubname());
    long result = mDatabase.insert(Subjects.TABLE_S, null, values);
    mDatabase.close();

    return result;
}

I create layout with field to input subject name and button to send subject name to database. This is code for that part:

mSubject = (EditText) findViewById(R.id.subjects);
    mSelect = (Button) findViewById(R.id.button_sub);

 mSelect.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            String username = mUser.getUsername();
            String subjectName = mSubject.getText().toString().trim();
            iSubjects.setUsername(username);
            iSubjects.setSubname(subjectName);
            //String subname =iSubjects.getSubname();
            Subjects subject = new Subjects(username,subjectName);
            long rowId = mManager.addSubject(subject);

            if (rowId == -1) {
                String message = iSubjects.getUsername()+""+iSubjects.getSubname();
                //"Not have anything insert to table! : ERROR!!";
                Toast.makeText(mContext, message, Toast.LENGTH_SHORT).show();
            } else {
                String message = getString(R.string.register_success);
                Toast.makeText(mContext, message, Toast.LENGTH_SHORT).show();
                finish();
            }

        }
    });

When I run the activity class.It show errors like this:

05-04 00:00:45.245  13336-13336/com.example.cash.app1 E/SQLiteLog﹕ (1) no such table: subject
05-04 00:00:45.253  13336-13336/com.example.cash.app1 E/SQLiteDatabase﹕ Error inserting username=c subjectName=asd
android.database.sqlite.SQLiteException: no such table: subject (code 1): , while compiling: INSERT INTO subject(username,subjectName) VALUES (?,?)
        at android.database.sqlite.SQLiteConnection.nativePrepareStatement(Native Method)
        at android.database.sqlite.SQLiteConnection.acquirePreparedStatement(SQLiteConnection.java:889)
        at android.database.sqlite.SQLiteConnection.prepare(SQLiteConnection.java:500)
        at android.database.sqlite.SQLiteSession.prepare(SQLiteSession.java:588)
        at android.database.sqlite.SQLiteProgram.<init>(SQLiteProgram.java:58)
        at android.database.sqlite.SQLiteStatement.<init>(SQLiteStatement.java:31)
        at android.database.sqlite.SQLiteDatabase.insertWithOnConflict(SQLiteDatabase.java:1469)
        at android.database.sqlite.SQLiteDatabase.insert(SQLiteDatabase.java:1341)
        at com.example.cash.app1.UserManager.addSubject(UserManager.java:131)
        at com.example.cash.app1.SubjectActivity$1.onClick(SubjectActivity.java:58)
        at android.view.View.performClick(View.java:4756)
        at android.view.View$PerformClick.run(View.java:19749)
        at android.os.Handler.handleCallback(Handler.java:739)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:135)
        at android.app.ActivityThread.main(ActivityThread.java:5221)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)

I don't know what wrong with my code. I have tried to fix it by follow many website and many forums but it doesn't work. Any help is greatly appreciated. Thank you :)