How do I tell my parent I'm transgender, and that I am not their daughter, but their son?

I am struggling with hiding my true self. I recently chopped off all my hair in secret, due to not being able to stop myself. I feel suffocated and trapped….. My parent doesn’t know, and the first time the subject of me being trans came up, they told me I was confused (two years ago). I felt discouraged, and convinced myself that I was a girl for a while, but it didn’t feel… right. I then decided that I was non-binary. But a part of me knew the truth. You know the feeling when you have a pillow over your face, but you try breathing through the pillow? Well that’s how I feel. I feel suffocated and trapped in my own body. When I finally came to the conclusion that I wasn’t a girl, and that I wasn’t non-binary, I felt sorta in control…. But I am reminded every day that I am in the wrong body and that no one will see me as a boy when I look in the mirror. I cut my hair, but I have to cover it with a hat, or else my parent will know, and I am scared, because when they do find out, thay will have to ask why? Why I would cut my hair short. And I would not be able to hold it in anymore. I would have to tell them. I just don’t know how, without them over reacting…. Please help.