...as far as the holy mother church is concerned you can't leave it. and nobody asked you to join.
So you were never Confirmed? -- that point at which you choose for yourself to be of the faith. You do understand that at your Baptism your Godparents made your choice in proxy only, in advance of that time where you make the choice for yourself as a young adult. As for "nobody asked you to join" what did you think Confirmation was?
If it was merely a social requirement for you, something your parents and nuns told you to do, then that was wrong. I'd guess for you it should have come later, as a young man. That doesn't mean that, as an adult, you can't make that former social event something more genuine by now. But you'd have to want it, another free-will choice yet offered to you.
PM is more appropriate here. Let's not bother our fellow Christians with technicalities of doctrine, the Catholic faith is not the end-all / be-all of Christian faith after all.