Coming in late (and also new here) but are you in a position where you have to tell them? Insurance wise, living situation wise, etc? Not that I'd advise lying to your parents unless you have to, I didn't tell my parents until they found out by accident over a year later, and they weren't happy about it... but ultimately, if you're in a position where you're able to, I don't feel like we have to justify ourselves to anyone.
Otherwise, could be worth talking to a therapist about (if you can find a good one and that's something that is available to you). If not to help you come out, just to say that you've talked it through with someone else and still want to go through with it. Only suggesting that if you feel it'd help though, because that's a lot of effort just to figure out what you already know.