Moving in with my boyfriend at 18

Hi. I’ve always believed that marriage should come first before moving in with the opposite sex but after dating my boyfriend for 3 years that belief is starting to change. my boyfriend, doug, and I are very very close. we can be our true selves around each other. I’m more comfortable around him than most of my friends and I never feel that I’m getting judged around him. he’s 21 and has been moved out for 3 years now so to him it doesn’t seem like any big deal for me to move out. but to me it’s a little different. my parents and I have a pretty close relationship and I think a pretty mature one. some of my friends still fight with their mom about stupid stuff, but I’ve been over that for about a year. I’m scared to bring it up because I don’t know what kind of a reaction it will bring. they love doug as if he was their own child and they know how much we care for each other. I know my parents were in the same situation when they were dating, same age difference and everything, but they didn’t move in until they were married. I also know that statistics say that couples who move in together are most likely to break up before marriage or if they do get married after they move in it only takes 5-7 years for a divorce to take place. I don’t really understand those statistics because everyone and every relationship is different. if there is any advice you have or a way to talk to my parents please help!

Thanks :)