I have a new girlfriend but my parents don't know I'm gay

I couple months ago I met a girl that I'm very interested in, and it's the first time I've connected so well with someone. We're both very interested in each other despite living a few hours away from each other but we're at the point now where we've decided to pursue things.

It was around the time that I met her that I started coming out to a few people. My parents however still don't know that I'm gay. I'm 20 years old and live at home, so privacy is pretty difficult. I went to see her a few weeks ago and my parents know that I slept over at her house. If they knew things weren't platonic they wouldn't have been okay with me sleeping over, even though I'm 20.

In a couple weeks, she's coming here for the weekend and I plan to spend the entire weekend with her, including the nights. I'd really like to tell my parents, even though I'm a little bit scared. The problem is that I don't know how I can tell them before she comes, and still be able to spend the night with her. I'm an adult and ultimately they can't say no, but finding out their daughter is gay and sleeping in another girl's bed might be a bit much for them all at once. On the other hand, if I wait until after to tell them, they'll know that I've spent the night with her three times without their knowledge.

I just need some advice on what the best approach might be to this situation. Thanks for taking the time to read and respond!