Sequence diagram with web-facing MVC!

Good Afternoon folks, I'm having second thoughts about some sequence diagrams I'm developing for a college job.

In theory I already know what a sequence diagram is, what it does and what its purpose, but the problem comes when it comes to modeling the same!

I will paste my use case and just after how the diagram is:

USE CASE: SCHEDULE QUERY LEAD ACTOR: SECRETARY

The use case begins when the secretary needs to schedule an appointment for a particular patient; The secretary clicks the "Find patient" button on the appointment scheduling page. The system directs to the search page for registered patients. The desk types the patient's name or part of it and presses the "enter"key. The system displays in a table the patients found. The secretary marks the checkbox of the respective patient and clicks the "Confirm"button. The system returns to the scheduling page of QUERY. The desktop clicks on the calendar icon in the "date query" field. The system displays the available dates of the current month. The secretary selects the desired date. The desktop clicks on the calendar icon in the "query time" field. The system displays the available hours of the selected date. The desk selects the desired time. The desk clicks the "schedule" button. The system returns the message "successfully scheduled query".

The problem is that I'm finding things missing.

Remembering that I'm modeling the project trying to use MVC architecture and that the project is a webapp! Any suggestions? Photos of wireframe