It is certainly time to open up to your parents and discuss the fact that you feel called to serve god within the ministry of the church. A friend of mine felt called to the priesthood, it took him about eight years from the time he entered the seminary, to the time he took his priestly vows. In that time he not only discussed his calling with his parents, his priest and spiritual advisers, he also examined it with friends whose spirituality he trusted, though none of us was contemplating any form of holy orders.
A commitment to god, in a public ministry is a wonderful gift. As a lay person, I have seen and experienced, the joy a deeply religious priest can bring to a congregation. Unfortunately, I’ve also seen the destruction a lukewarm priestly faith can bring to those entrusted to his care. Though, we as Catholics should not allow our faith to rest on the actions of individual men, I’ve known people turn away from the church because of the actions and sometimes lack of compassion shown by their priest.
What I’m trying to say is that yours is a wonderful first step but the road to priesthood needs to be carefully and prayerfully navigated. A reluctance to discuss your decision with your parents may be indicative that you are at the very beginning of this journey. A priest needs not just faith, he also needs plenty of courage.
When James and John asked Jesus if they could be his second in command his reply was, "But Jesus said to them, “You don’t know what you are asking! Are you able to drink from the bitter cup of suffering I am about to drink? Are you able to be baptized with the baptism of suffering I must be baptized with?”
Mark 10:38
I say these thinks not to discourage you, but hopefully to help you understand that you are being called to a difficult path. You will need lots of help, support and prayers and great courage, hopefully some of this can come from the two people who probably love you most, your parents. All the best.