Is my website being crawled?

I have a mean-stack website hosted in a DigitalOcean & nginx & ubuntu server.

In the website, there is a webpage with a button to allow users to send me a message:

<button type="submit" class="btn btn-lg btn-theme" ng-click="mySubmit()">Send Message</button>

in the controller:

$scope.mySubmit = function () {
    return $http.post('/httpOnly/request/addRequest', { "name": $scope.name, "mail": $scope.mail, "message": $scope.message })
}

Then, in the backend, it uses https://github.com/sendgrid/sendgrid-nodejs to send me emails.

Previously, everything was fine. However, for 1 week, I received every day 7 mails in a row with undefined values. The 7 mails arrived at almost same time every day.

Does anyone know what is happening? Is my website being crawled? If so, is there a way to avoid that?