Gwencook,
I'm not sure if you're looking for any ideas/help/... but I have a suggestion that helped me to come out to a ton of people. I didn't use the work Transgender, ever. I let them make that leap. I was diagnosed with Gender Dysphoria which sometimes pushes people to transition.
I think asking your stepmom to help you find a therapist to work through everything might also be a direction you can go. Let a therapist decide if you have gender dysphoria. Let them do their job, don't walk in and say "I have Gender Dysphoria." Talk with them and be honest. If you don't tell them everything and being honest you'll do nothing but waste your time and money. Therapy is helpful at getting your thoughts in order.
Good luck and I hope all goes well
Denise