How to get identified contacts from xDB taking into account if one already exists

ContactFactory.cs

private ContactRepository contactRepository = Sitecore.Configuration.Factory.CreateObject("tracking/contactRepository", true) as ContactRepository;
private ContactManager contactManager = Sitecore.Configuration.Factory.CreateObject("tracking/contactManager", true) as ContactManager;

public Contact GetContact(string emailAddress)
{
    if (IsContactInSession(emailAddress))
    {
        return Tracker.Current.Session.Contact;
    }

    var existingContact = ContactRepository.LoadContactReadOnly(emailAddress);

    Contact contact;
                
    if (contact != null)
    {
        LockAttemptResult<Contact> lockResult = ContactManager.TryLoadContact(existingContact.ContactId);

        switch (lockResult.Status)
        {
            case LockAttemptStatus.Success:
                Contact lockedContact = lockResult.Object;
                lockedContact.ContactSaveMode = ContactSaveMode.AlwaysSave;
                contact = lockedContact;
                break;
            case LockAttemptStatus.NotFound:
                contact = Tracker.Current.Session.Contact;
                break;
            default:
                throw new Exception(this.GetType() + " Contact could not be locked - " + emailAddress);
        }
    }
    // if Contact in session's identifier is set and not equal to email address create new Contact
    else if (Tracker.Current.Session.Contact.Identifiers.Identifier != null
        && !Tracker.Current.Session.Contact.Identifiers.Identifier.Equals(emailAddress, StringComparison.InvariantCultureIgnoreCase))
    {
        contact = contactRepository.CreateContact(ID.NewID);
        contact.System.Value = 0;
        contact.System.VisitCount = 0;
        contact.ContactSaveMode = ContactSaveMode.AlwaysSave;
    }
    // Contact in session's identifier is null use that Contact
    else
    {
        contact = Tracker.Current.Session.Contact;
    }

    // If the matched Contact is not as the same as the Contact Sitecore loaded into session 
    // or the Contact in session is not identified
    // then we need to call .Identify() - more on this later
    if (!contact.ContactId.Equals(Tracker.Current.Session.Contact.ContactId)
        || (contact.ContactId.Equals(Tracker.Current.Session.Contact.ContactId) && Tracker.Current.Session.Contact.Identifiers.Identifier == null))
    {
        Tracker.Current.Session.Identify(emailAddress);

        // Contact has been updated via Identify so update the reference
        contact = Tracker.Current.Session.Contact;
    }

    return matchedContact;
}

private bool IsContactInSession(string emailAddress)
{
  var tracker = Tracker.Current;

  if (tracker != null &&
    tracker.IsActive &&
    tracker.Session != null &&
    tracker.Session.Contact != null &&
    tracker.Session.Contact.Identifiers != null &&
    tracker.Session.Contact.Identifiers.Identifier != null &&
    tracker.Session.Contact.Identifiers.Identifier.Equals(emailAddress, StringComparison.InvariantCultureIgnoreCase))
  {
      return true;
  }

  return false;
}