Flutter Web/Firebase - Pressing back in browser bypasses verification process

When my user signs up I direct them to a page to inform them that they need to verify their email before continuing:

Here is my verification screen code:

  class VerifyScreen extends StatefulWidget {
  @override
  _VerifyScreenState createState() => _VerifyScreenState();
}

class _VerifyScreenState extends State<VerifyScreen> {
  final auth = FirebaseAuth.instance;
  User user;

  Timer timer;

  @override
  void initState() {
    user = auth.currentUser;
    user.sendEmailVerification();

    timer = Timer.periodic(
      Duration(seconds: 5),
      (timer) {
        checkEmailVerified();
      },
    );
    super.initState();
  }

  @override
  void dispose() {
    timer.cancel();
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Container(
          height: MediaQuery.of(context).size.height * 0.8,
          width: MediaQuery.of(context).size.width * 0.8,
          child: Text(
              "An email has been sent to ${user.email} please verify before proceeding"),
        ),
      ),
    );
  }

  Future<void> checkEmailVerified() async {
    user = auth.currentUser;
    await user.reload();

    if (user.emailVerified) {
      Navigator.of(context).pushReplacement(
        MaterialPageRoute(
          builder: (context) => OurHomePage(),
        ),
      );
      timer.cancel();
    }
  }
}

Problem Statement: When I press the back arrow on my chrome browser:

I get returned to my homepage with the user signed in which I don't want. I would like my user to verify their email before being able to continue. Here's the drawer on my homepage after I press the back button without verifying the email:

I use provider to pass my user object around my app. Here is my main.dart:

  void main() async {
  WidgetsFlutterBinding.ensureInitialized();
  await Firebase.initializeApp();
  runApp(
    MultiProvider(
      providers: [
        Provider(
          create: (_) => FirebaseAuthService(),
        ),
        StreamProvider<OurUser>(
            create: (context) =>
                context.read<FirebaseAuthService>().onAuthStateChanged),
      ],
      child: MaterialApp(theme: OurTheme().buildTheme(), home: OurHomePage()),
    ),
  );
}

I then user Consumer to consume that provider on my Homepage:

class OurHomePage extends StatefulWidget {
  @override
  _OurHomePageState createState() => _OurHomePageState();
}

class _OurHomePageState extends State<OurHomePage> {
  @override
  Widget build(BuildContext context) {
    return Consumer<OurUser>(
      builder: (_, user, __) {
        return ChangeNotifierProvider<SignInViewModel>(
          create: (_) => SignInViewModel(context.read),
          builder: (_, child) {
            return Scaffold(appBar: AppBar(title: Text("My Homepage")));
          },
        );
      },
    );
  }
}

Can anyone help me resolve the issue I'm facing? Thanks in advance.

On homepage check if user is logged in and when is, check if he has verified email. If he has, let him in, otherwise show him some message.