I'm worried about telling my parents I don't want to be part of Catholicism anymore
How do you think they will react?
They will be angry at me.
They will need to learn to respect your differences in beliefs. It is not uncommon for children to stray from they path their parents expect them to take.
I hope they understand.
I'm sure your parents will see that your beliefs are different than theirs, and won't hold that against you. There's no reason for you to take part in something just because your parents expect you to.