Hard dissagree. It's wrong in Nebraska, wrong in Germany, and wrong everywhere else where the standard is some date before birth.
I can't say this is something I have experienced. I got gender euphoria from the start right up to today.
But maybe you are gender fluid? If that fits then it fits. It's OK to be a man on Tues and a woman on Friday.
There is no wrong way to be you. There is only you. The words are only important if they are useful. When words fail, you are still here, and you are more important than the words will ever be.
It's OK to tell a story to simplify it down to strangers. (Like: I'm a trans woman) You don't need to have the whole experience of your transition down to an elevator speech.
I say this to give some guidance on how you could move through the world. Strangers get the simple lie. Friends and family get the more nuanced truth.
Your mother is saying nonsense. My mom knew I liked girls when I was 4. She thought that was normal, because I'm a trans woman, but it was obvious even then.
I'm sorry. You don't deserve invalidation. You deserve affirmation. You don't owe your mother anything, but it's possible that your dad or a grandparent can be an ally for you with the rest of the family.
How can you tell them? I don't know. "Hey, I have something important to tell you." Will probably force the issue.
You don't have to come out, but if you want to, that's how I would start.
So, you are on the right track to assert that the only person that can say you are trans is you. At best, we can give you things to think about.
First, you focus on your body, and mention your weight as unsatisfying. If you lost a bunch of weight and worked out every day, what would make you happier? A muscular, masculine body? With big shoulders and strong arms and thighs? Or would you preferred a smaller, athletic, feminine body? That still had some fat in your breasts and butt?
Would you like a soft feminine face? Or a handsome, masculine face?
If that doesn't make it obvious, what about relationships? Would you like be your parents son? Or their daughter? Would you rather be a girlfriend? Or a boyfriend? If you get married, would you like to be the bride? Or the groom?
If you have children someday, would you be comfortable as their dad? Or their mother?
"Neither" is also an option. Maybe you are non binary or agender.
I hope this helps you to consider what you want for yourself. None of these questions can 100% guarantee you are trans, but each can offer evidence one way or the other.
“(your) right To swing your fist ends just where my nose begins”
Exactly, If you care so much transplant it into your uterus.