Privacy of employer sponsored medical insurance

My employer provides a medical insurance. One section of the enrollment form asks existing medical problems, treatment, medication, etc. The form prints “this confidential information will not be seen or given to your employer” and “after completion, please remove the tap and fold close to seal”, which I did. But a few days later, my employer asked me specific question regarding what I filled to the form, such as what the dosage of the medicine I am taking, etc. Does this violate my privacy?