I assumed the OP was female from their concerns about later marriage. This is not a typical 15 yr old male concern. If my assumption was wrong, please accept apologies, no slight was intended.
It struck me since posting, your conscience about getting confirmed, your folks have the same conscience about you taking the ccd classes. So, they cannot let you not attend the classes, just like you can’t accept confirmation.
Regarding what I wish I’d have sought before I left - well, I did skip ccd classes for many years, not just the pre-confirmation classes. I spent a few years, maybe 13 to 16, as an atheist and then had a conversion experience in an evangelical church in the Wesleyan tradition. It actually happened at a retreat I went to in order to spend time with a girl.
OP, I wasn’t planning to, but I’m going to share most of my story with you here, because I respect Easterjoy (I hope I’m remembering her name right) and it feels right to do so. See, now I’m a lapsed agnostic - not atheist, agnostic. Perhaps even a formal agnostic, because, as a scientist, I know that I cannot know most things of a religious / spiritual nature. So, I can neither know, nor know not. But I try to respect my intuition, because maybe it is something more. Hopefully, when I finish getting this down, I’ll have answered Easterjoy’s admonishment.
Anyhow, the girl dumped me pretty much right after my conversion experience. Like, at the retreat still dumpage. So, I asked for a Bible to read, one of the pastors gave me his. A black hardcover NIV - strange the details you sometimes remember. Opened it to the middle and first book I read was Job.
This was a good choice, because, what I felt, after the initial ecstasy of conversion? It was pain. See, my father, at this time he was a non-drinking alcoholic. Later in my life I’d go to open NA meetings to get help with cutting myself. Point is, if someone wasn’t drinking and trying to fix what was wrong in the first place I’d call them a recovering alcoholic.
I ended up at a Wesleyan college near a Franciscan college. I ended up at an intercollegiate retreat at the retreat center associated with the Franciscan college. When asked at the time why I went, I’d say because God asked me what I would do if called to the priesthood. It was a magical place, and I returned for Sunday Mass there semi-regularly. I also spent a holiday break there because I couldn’t stay home. Holidays were hard for me; my peers would share their excitement to be able to go home to visit family; I suffered silently that I had to go home, because the dorms closed.
Ironically, it was at this Christian that I had doubts again. Doubt is not quite the right word. I decided that a merciful God would assign people afterward to where they would be best suited and that perhaps there are those who are so damaged in this life, that, while not deserving of punishment, might find ever-communion with God and others itself painful. For those people, my faith was that God would care for them in the best possible way, though I know not what. I suspected I was such a person and had faith I would be cared for afterward. I graduated and thought less and less about spiritual matters until about five years ago, when I had cause to answer whether I believed in a god and the immortality of the soul. Shortly after that, my little girl was born.
I can’t quite honestly say I hope she is raised Catholic, so no baptism. I do want her to have some exposure ro a moral code; I don’t think I would be me without the path I walked. I thought about getting her into ccd classes without receiving sacraments, but most folks said that would be weird, as ccd is sacrament prep. Maybe I’ll get her involved with the Jewish community, let them do their job of being an example of righteousness.
I don’t think I’ve answered Easterjoy’s admonition, but I just don’t know what I would have liked to know back then. I’ll close with two things - if your folks aren’t bad people, well, you need to become your own person now, and this process is not always smooth and painless, but don’t cast away a relationship with them - let it change over time, just don’t throw it out. If theyare bad people, well, if they were, you wouldn’t be here posting about confirmation doubts. Also, be respectful of things sacred to others, even if not sacred to you. An example, when I go to Mass now and then at this point in my life, while the genuflexion does not have meaning ro me, I do bow toward the altar whenever a genuflexion is called for, to give respect to the sacred.