Dear Marie,  

There are three terms to keep in mind in this regard: chastity, celibacy and virginity. Each means something different, but they are often confused. 

Chastity is the proper use of the gift of sexuality. It has an internal and external dimension; the internal has to do with our thoughts, desires, etc, and the external has to do with our actions. Chastity is a virtue, and everyone is called to be chaste, and the form that chastity will take depends on the particular vocation of the individual (fidelity to one another, giving themselves to one another, respect for one another and openness to life are some aspects of married chastity, for example). Celibacy is a form of chastity that is lived by those who are not yet married and by those who have taken a life-long commitment to it (like nuns, priests) and it consists in abstinence. Virginity is the state of a person who has not yet had intercourse.  

If a person faults against chastity he or she can recover the virtue by going to confession and leaving their fault behind. Many of our faults against chastity are internal, and so a person can have struggles and failings in chastity without losing their virginity, the physical state of which cannot be recovered if one loses it.

Today you will hear talk about "recovered virginity", which spiritually speaking is an uplifting thought. It reminds us of the fact that when we confess our sins sincerely, receive absolution and make a firm resolution, God does not look back and we shouldn't either, unless it is to learn a lesson in prudence and humility.

To be a nun you need to be chaste externally and internally, and to consecrate your life to God in celibacy. God bless.