Snowboarding, hi. Welcome to the forum. Please note that I'm changing the title of your thread to actually reflect the contents; this will get you more replies. Also, I'm putting an indication for spoilers in your title. If you'll read the sticky thread at the top of the forum, you'll see that we've gotten a lot of complaints from gamers who don't want to open threads unknowingly, only to find information they'd rather learn on their own. Please take that into account on your next thread.
As to your question: you can't enter the Leviathan before finding 4 star maps. After you've discovered the fourth, your next trip into space automatically has the Ebon Hawk pulled into the Leviathan. I'm not sure, therefore, what you mean by "doing things backwards." Perhaps you can explain what you did. Have you played through, before?