Hi oZma,
Firstly I'd like to say that I'm very sorry to hear you're having such a hard time, it totally sucks to feel crappy about yourself. I've certainly been there and I know it's very hard to hear advise from anyone and take it to heart, even if you're asking for help. Please know that I respect your right to feel any way you choose and that it isn't stupid to feel the way you do. Your feeling are a completely valid lived experience, and just because the rest of think you're gorgeous doesn't mean you don't have a very good reason to feel down.
What I hope I can help you with is understanding why you feel the way you do in the first place because I think if we can understand how we get to where we are emotionally, it can provide us with a map to get to somewhere better.
I'm going to concentrate on two main parts here and I want you to understand that these are facts, not opinions, so if you wish to dismiss them you must also accept that you choose to live in an unhappy fantasy rather than reality. I grant you however that many, many people choose their own fantasy rather than have their ego face the shame of having been wrong about anything ever.
So, onto the good stuf.
How we learn to be who we areWe tend to think that we are conscious agents in the story of our lives and that we go around making decisions but the truth of the matter is actually rather different at a neurological level.
Firstly we need to understand that the body, and especially the brains most favouritest thing in the whole world is Heuristics.
A Heuristic is basically a short cut and it's totally awesome, except when we later find that we're using it for something that it turns out is bad for us.
Here's how it works.
Any action we perform is triggered by a cascade of neurons firing in a specific sequence. Change a few neuron along the chain and we'll perform basically the same action but with some slight variation.
To get to that point however, the synapses between our neurons have to reach a threshold state.
That's the point when there's enough messenger chemicals (dopamine, Acetylcholine, norepinephrine, Serotonin) floating around in the synaptic gap that if any more are added, it will trigger any other neurons that are touching that synaptic gap to fire.
An electrical impulse is then carried along those neurons to all the synaptic gaps they are connected to causing the release of more messenger chemicals into those synaptic gaps until one of them reaches it's threshold state and the chain continues.
Each time a neuron it caused to fire by it's threshold level being reached it becomes more sensitive, thus lowering the threshold limit and increasing the likelihood that it will be the first to fire the next time.
In simple tearms, anytime we perform an action it gets easier (the neural threshold is lowered) for us to perform the same action next time. This is the biological underpinning for "Practice makes prefect".
Our sense of conscious self seems to be there to "moderate" if you will. We do something, and then decide if it was good or bad.
If good, repeat (neurons get stronger) if bad, try a new set of neurons.
Here's where it becomes relevant to you.
We develop all our thoughts and opinions in the same way. There is no functional difference in the brain between a neural cascade that results in say, the movement of your hand, and one that results in you thinking about whether the Dalai Lama prefers chocolate or strawberry ice cream.
Now that last though wasn't very relevant to most of our lives so we probably won't think about it again and thus the neurons associated with it won't get fired very often (except that now every time you see strawberry and cocolate ice cream together you'll probably end up thinking of the Dalai Lama

)
By contrast. there are many things that we think about all the time, in fact they're so much a part of the landscape of our thoughts that often, we don't even notice that we're thinking about them!
Which brings us back to Heuristics.
Everything about the way our brain is set up is designed to make any action that we do frequently enough, happen subconciously.That's great for allowing you to use a knife and fork to eat your dinner while holding a conversation at the same time. It sucks when it allows you to start listing off reasons you fail art being a girl with no more effort than getting a bite of food to your mouth.
The problem is, both activities feed the brain in the same way.
Now, onto the second big influencer on how you think.
PatriarchyI think one of the things you're experiencing right now is actually way more Cis than you realize.
Feelings of crushing inadequacy.
Congratulations, you're just like a genetic girl.
You see, we don't really get to choose
what we think about, only
how we want to think about it. But even in forming our opinions about what the world gives us to ponder, there tends to be a fairly implicit "and you should feel this way about it" tacked on.
Patriarchy basically pathologizes being female, and that opinion is handed to us every day in a whole bunch of different ways.
Those thoughts get into our heads and unless we're really paying close attention, heuristics makes sure we never need to consciously examine them.
What's worse than being a woman according to patriarchy? Being a man who says they want to be a woman!
"OMG!" says patriarchy, "you must be sooooo F'd up!"
"oh, and while you're at it, here's several thousand years worth of culturally ingrained reasons to feel inferior and compete with other women over things men care about."
The other thing patriarchy does, like any colonialist model, is to separate the oppressed group into more and less oppressed subgroups.
Those of us who are trans tend to be toward the bottom of those groups.
In the same way that GGs often accept the limits placed upon them by patriarchy, we have a tendency to do the same.
It's worse for us because most of us spent time living as males which often meant faking male, pro patriarchy opinions. The big problem there is, that whole "fake it till you make it" things actually works so as women we tend to be loaded down with way more sense of inadequacy than genetic girls who at least grew up in a sisterhood of support to help fight back against those received opinions that make us feel so bad about ourselves.
So what can you do about it?
Refuse to be a victim! Recognize that those negative thoughts you have don't reflect who you are, only what society tries to make you be. Fight back, get some righteous anger going about the injustices you've been dealt. Understand that your emotions are there to help you. Even the ones we like to call "negative" are a part of your bodies beautiful system of balancing itself.
When you feel sad, don't dwell in the sadness but see it as a call to let go of thoughts and emotions that are constraining you.
When you feel angry, recognize that anger is there to help you rebuild your boundaries so that you have a safe space to be you in.
Your emotions are your friends and beloved allies, they call your attention to the wonders and the injustices of the world.
The next time you reel down, heed the call of your emotions and take action rather than surrendering to negative thoughts that aren't even yours but were just handed to us all on day one as a part of the "inadequate reality starter kit".
I hope some of that helps even just a little and remember that you are loved here.
*huggs*