Moving out with my boyfriend

My boyfriend and I have been together for 6 months. Recently we’ve been talking about marriage and moving in together. We’re both catholic and I have very strict catholic Hispanic parents and I’m really nervous to even mention it to them. I get in trouble if I get home past 10, like they even lock the doors on me. So imagine me telling them I want to live with my bf. I’m 20 and he’s 19. He says he wants to get secretly married by court before moving in because catholic...but I told him we’ve already had sex and done stuff that go against that. It’s a huge decision and he’s super serious about it. I want to do it but I overthink and there’s a lot that consider. I just don’t know what to do or how to even begin this process. How would I even tell my parents? I feel like they’re going to shun me or keep me from moving out. I also have a 25 year old sister that feels she needs to dictate every part of my life.