I'm scared tomorrow morning before he goes to work he will find out that I am transgender I am so scared
Hi there! Given that you have the support of your step mom, you can continue to count on her for support. Is she the one who will talk with your dad tomorrow morning? (*hug*)
If you feel it is too early for your dad to know, ask her to give you a bit more time. Hope it all goes well for you.
Its not too early because eventually he will need to find out so its better for him to understand and get it in his head this is who I am now than delay it in my defense he will be loosing a son but gaining a daughter ^_^