Dude. i'm in the same situation as you, everyone thinks I'm 10-12 and that I don't belong in high school. I've managed to keep up a short-term relationship with a cisgirl, but then things turned ugly because my friend tried to help me out and make her stop being so clingy by saying I dated a guy. I went with the whole thing because I wanted to feel normal, knowing that I wasn't going to let it progress no matter what, and hated being selfish and not telling her. It hurts whether you do or you don't with cisgirls who know nothing of trans issues- unless they're accepting and willing to overlook your parts, then you either have a weirded-out girl who makes you feel awful or the guilt of not being able to tell her or do something with her if you wanted to eats at you. It all eats at you- if you let it.
You don't have to let it. Dysphoria is a nagging b*tch but you can actually tune it out, you're taking a defeatist approach to the whole thing. Venting is cool, but it's only helpful if you work on changing what you can to decrease the negative in your life as much as possible. Everybody vents once in a while, but then they move on. Me? I've come to deal with the "OMG YOU'RE A SENIOR?! BUT YOU'RE SO TINY!!!11" comments because it isn't worth my time worrying about it. I've got bigger issues, maybe not everybody deals with their joints being ripped apart on the inside but it puts things into perspective for me. The damage being done is permanent; the dysphoria I feel right now is temporary. So is yours. One day you're going to look yourself in the mirror and be okay, so long as you don't let it get to your head now. We're here for you, man.
By the way, I know how it is with the parents. My mom screams at me all the time and has breakdowns over the tiniest trans-related thing because she can't comprehend me being a "freak" and thinks I'm just confused and a lesbian. My dad is horrible and makes fun of me about it all the time, and I don't even see the rest of my family but they wouldn't support me either. There's no adult for me to turn to who will lend an ear or offer advice. That's why I come here, where people don't act like jerks to me and tell me that presenting as a boy is "false advertisement". You want change in your life? Take it for yourself. Tell people, one by one, to call you Brandon and use male pronouns. Get some support- students, teachers, staff, whoever will listen and accept you. Once someone enforces it, others will follow suit, and if anyone decides to be dumb and go against it that's their problem. You have an issue, you take it to someone in the school who can resolve it. Your mom doesn't have to agree with it, but if you can, give her reading material to try and help her understand at the very least what you're going through.
Best of luck. I haven't gone back to school yet, but when I do I'm going to try being out or stealth with teachers. I'm terrified of the thought but in the end, it's my right to be who I am, and the same holds for you. Only good thing about waiting is that it means science develops more, and while the phallus that we can have created isn't perfect, it's pretty close. Who knows, maybe in our lifetime they'll come up with a way to create one that "works" without needing a pump and all. But yeah, try to find anything you can to take your mind off of what you don't have. I find that it helps to go along with people's assumptions and play the part of little kid. I don't even "feel" trans anymore because I've settled into a niche of being stealth, and I'm pre-T too. It's definitely doable if you play your cards right.