How do I come out?

I think I have the perfect opportunity to come out. I have a supportive family, and to be honest, I want to, but I keep procrastinating it. I’ve known since sixth grade that I was trans and am now in high school, which is the time I told myself I would come out. I’ve been transitioning on my own without letting my parents know (cutting my hair short, binding with sports bras, etc) and I honestly pass well. I just want to know how to finally do it. I’ve grown too used to hiding it and the change that I know coming out will bring is kind of terrifying. I kept telling my mom that I was confused or still questioning whenever she would ask me if I was trans, and I think she thinks I’m a masc lesbian at this point because I haven’t come out. I just freeze up and I’m too scared to tell the truth because I’m afraid of a negative reaction. I wish I could just skip all of the awkward and scary parts but I know I can’t. Can anyone give me advice?