Muscle Weakness and Brain Control in Rare Disorders - Rare Disease

Muscle strength is often difficult to achieve and requires brain control?

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Currently diagnosed conditions include: 1.
Right chest depression, 2.
Flat feet, 3.
Knee deformity (the physician noted that one leg appears X-shaped while the two legs cannot be aligned like an O shape).
I have observed the following issues for many years through experiences such as crowded public transport, outdoor activities, and daily life in class...

Q1: I don't understand why.
I do 100 push-ups every night before bed, but my arms struggle to exert force and feel very weak and shaky.
For instance, when my classmates write, their muscles are tense and their tendons are visibly prominent, while I can only achieve muscle firmness through conscious control.
Additionally, when I take out the trash, my hand trembles and gradually loses strength, but as soon as I switch to my left hand, my right hand immediately returns to normal.
My writing lacks power and appears messy because of my limited range of motion; I have to consciously control my arm to make it firm, resulting in neat and strong handwriting.
However, this distraction makes it difficult for me to listen and take notes during lectures.
Furthermore, when I rest my hands on the table, the tendons near the joints make a noise as they press against the table; that tendon is very relaxed, unlike my classmates who do not experience this.
Q2a: I run and ride a stationary bike daily, but I also struggle to exert force below my waist.
When standing, only my calves feel firm, while my thighs and glutes are soft.
I can easily press down and feel the bones beneath.
The tendon above my heel is not prominent and is soft, unlike my classmates who have noticeable and resilient tendons.
When I stand on the bus, I often sway significantly and find it hard to maintain balance, but if I focus my mind on standing, I can manage.
Walking is uncomfortable for both feet, especially near the joints, and going up stairs is even more painful.

Q2b: During military training classes, the instructor commands everyone to stand at attention, tightening the glutes and engaging the core.
I can tighten my glutes, but only briefly, as I tend to relax when my mind wanders.
It feels like my intestines are about to fall out, and I find it difficult to maintain prolonged tension.
My glutes are also hard to engage, appearing very saggy and soft, unlike my classmates who have firm and compact glutes, even those who are thin.
Therefore, wearing jeans that showcase muscle definition looks very unflattering on me, which is odd since I am young and active, yet my glutes sag.
Q2c: Sitting is also problematic; my glutes do not actively engage.
When sitting on the school's wooden chairs, even slight movements produce noticeable creaking sounds from the bones and nerves pressing against the chair.
I experience pain after a short time, and my legs easily go numb.
However, if I consciously engage my muscles, I can avoid compressing the nerves and bones, making sitting comfortable, but this does not last long, and I become soft again when I focus on class.
When my feet are resting, if someone brushes against them, they easily shift position, while my classmates remain stable and their feet do not move.
This has also made it difficult for me to ride a bike; during practice, I have nearly had serious accidents multiple times, almost falling off when accelerating or braking, and I struggle to maintain balance at red lights.
The muscle engagement in that position is also challenging, but when I focus my mind, everything returns to normal, though it does not last long.
Q2d: When I sleep, I lie with my feet together, with the soles touching the bed at a 180-degree angle.
Normal individuals have a certain angle, but mine is severely beyond the range.
I often experience numbness after a short time and frequently suffer from insomnia.

Could you please tell me what these conditions might indicate, doctor? I worry about this every day; I cannot understand why, at almost 19 years old, my situation is so severe.
I am in worse shape than classmates who use bikes for transportation or those who stay up for 1-2 days playing video games.
I have been aware of these issues since childhood, but I did not understand them back then and thought everyone was like this.
It was only when I entered group life in school that I realized my physical condition is quite poor.
I often lag behind in running and perform poorly in physical education, despite my efforts in training.
I only managed to place 10th out of 20 in a long-distance race.
It wasn't until I was 16 that I saw a doctor, but I may have consulted the wrong specialty.
It is impossible to explain all my issues in one visit, especially with many patients waiting, and I felt embarrassed to discuss some private conditions.
Even when I did speak up, I was laughed at by a few intern doctors nearby.
Ultimately, the doctor either prescribed painkillers or suggested I exercise more, or they simply did not understand my condition, advising me to focus on studying instead of pursuing sports.

Perhaps I appear normal on the outside, but in reality, my health is very poor, and many unexplained conditions are affecting my daily life.
I have taken numerous medications prescribed by Western medicine, as well as herbal remedies from traditional Chinese medicine, but my condition remains the same.
I truly hope there is a surgical solution to treat this, at least to have a definitive answer.
Thank you, doctor!

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Mr. Lin, 10~19 year old female. Ask Date: 2006/05/25