How I figured out what was wrong
Zephyr Breeze has always been a strange stallion. He has had multiple jobs however he always gets distracted thinking about his uneasiness. Every time he loses his job he goes home to his family. Especially his younger sister. Zephyr doesn't understand why but he has always been jealous of his sister. One day Zephyr's sister asks for his help in modeling a few suits for her friend Rarity. Zephyr only discovered his secret while he was helping out his sister's best friend Rarity in her boutique. Zephyr is helping Rarity by being a model for a few suit orders that's due in two days time.
Once Zephyr finishes modeling the last suit he hears Rarity say "Zephyr thanks so much for all your help modeling the suits. As thanks I will take you out to dinner as payment. If you will wait here for a minute I'll run upstairs and get changed. I'll be back in a few minutes. Feel free to look around if you want." Zephyr just stood there waiting for a minute before feeling the uneasiness return. Only this time he felt something else as well. It's like a compulsion or a strong draw of magic coming from somewhere in the boutique. As he follows the draw he sees that it was leading him to a beautiful Pink silk princess dress with long sleeves and a rainbow of diamonds sewn in. As Zephyr stares at the dress he gets absorbed and loses track of time staring at it. Before he could stop himself he trys on the dress.
Soon as he has the dress on he feels the uneasiness in himself lessen. Zephyr thinks for a second why the uneasiness lessened. Until all of the sudden it hit him why. The uneasiness,the jealousy for his sister, the fact most of his friends are mares and the feeling of how right the dress felt. It all leads to one conclusion. He wants to be a mare. Soon as he realizes this he breaks down crying. He's crying so hard he doesn't hear Rarity return.
Rarity upon seeing Zephyr in her specially made dress for Twilight sighs. However the second thing she notices is the tears in Zephyr's eyes. Getting worried she walks over to Zephyr and asks " are you okay Zephyr? You have tears in your eyes."
Zephyr jumps, hearing Rarity's voice next to him. After a few seconds passed so he could calm down enough to say " No Rarity I'm not okay. You see I was down here waiting for you to return when I felt a very strong compulsion or draw of magic that led me to this dress. As soon as I saw it I knew I had to try it on. For as long as I can remember I have always felt a very strong sense of uneasiness in me. I'm always jealous of my sister Fluttershy. All my friends are mares. Anyways as soon as I put this dress on I felt my uneasiness lessen. Once I felt that I started to think about why it would lessen and came to the realization that I am transgender. I am a mare on the inside. Once I realized that I broke down crying not knowing where to go from here."
Rarity looks at Zephyr in the eyes and sees them sparkling like a diamond. She takes a deep breath and says " Diamond, what you need to do first is come out to your family and your sisters best friends. That means me, your sister, Applejack, Rainbow Dash, Pinkie Pie, your parents and especially Twilight. The second thing you need to do is keep that dress. Third, you need to go home and come back here tomorrow at noon for a meeting with all of them."
Zephyr tilts his head at Rarity and asks " What did you just call me Rarity?" Rarity looks at Zephyr and answers " I called you Diamond because your eyes sparkle like a diamond in the light. Plus it sounds like a great name, Diamond Breeze." Zephyr thinks for a second before saying " I love it. Thanks Rarity. Can I trust you to get everypony here at noon tomorrow so I can tell them." After receiving a nod Diamond Breeze leaves to go home. That night Diamond was so worried she couldn't sleep very well.
At eleven the next morning Diamond put the dress on and fly's to Rarity's boutique. She arrives at eleven fifty and walks in. Once she enters the boutique she looks at everypony assembled and says " Everypony I'm transgender. I'm a mare on the inside but a stallion on the outside. Rarity thought I should come out to all of you first. My New name is Diamond Breeze. So what do you think?". Diamond looks at everypony before all of a sudden she is in a group hug with everypony accepting her for herself. Diamond Breeze smiles to herself and realizes that no matter what may come she can handle it with everypony by her side. Diamonds parents come over and say " Sweetie. We already knew that you were a mare. But since we are your parents we decided we would wait to see if you could figure it out for yourself. After all we could have told you but there was a very strong chance that you wouldn't believe us. Actually we decided that if you didn't figure it out within the next few days we were going to tell you the truth. We saw how it was destroying you mentally. We are so happy for you and we love your name. To be honest we were going to name you Diamond Breeze if you were born a filly."
Diamond couldn't believe what her parents just told her. Did they seriously know before she did. She thought about it for a few moments before accepting the fact that they knew and still accepted her for herself no matter what happens.