How to excel at math?

I know this question has been asked at least a hundred times earlier but before you mark this as duplicate please read this cause I seriously need some professional help here.

I'm a 15 year old kid who is pretty good at all other subject expect math. I am considered as smart but being self aware that I am not smart cause I am only just above average at math. I am a curious kid and I always was. I don't know where it went wrong but I failed somewhere.

Let me tell you something about my past. I started pre school at 4. I wasn't taught properly by my parents or family at home the only piece of education I got was from my school which was little less than four hours daily. I don't know if you guys are taught at home when you were young but in my local it it doesn't work like that every kid is taught from home more than that of school. But I remember that I was able to read and write way before than friends. I didn't care for math till recently because I was not challenged by it,I wasn't able to conceive it practical purpose which was clearly my teachers' failure I always ask my teacher "What this is used for ?" and she would answer "don't care about it". As I said am pretty curious and I think about everything so deeply, that's how I learn things.

I didn't attend school that much when I was young so I missed some basic arithmetic and I wouldn't ask anyone if had a doubt,I just pretended I knew it. I was always interested in science, especially physics I realised that it needed math so I started studying math last year even though I didn't like it. I also got interested in computer science recently and it need math too. So I've been pushing myself into studying it but it too obvious and I think it won't help studying if I don't love what I am doing.

I definitely got better at math recently cause I was terrible before. I got better at reasoning and problem solving lately but when it's from I syllabus I kinda fail. My teacher is good but she ain't the best,she just gives us many examples while not teaching a single bit of theory at all. I can't learn something clearly without knowing its meaning. Now let me compare my marks in math and other subjects,if I get 95 in science or any other subject, I would've gotten 85 in math. I don't know what's wrong with me, Am I math anxious or am I just stupid? As I mentioned above,I am kinda improving at math but i feel like it's not enough. I can go on and on but this is already longer than what I expected and I don't wanna make it tedious. I hope you will give me advices which would literally change my life cause I couldn't think of a career without mathematics.

I'm not sure whether people on this site (myself included) can give you better advice than people at school who know more about you than you have been able to summarize in your Question. So here are some things to think about. Perhaps take some as advice. Perhaps ignore others.

(1) I'm not sure whether starting to learn calculus at 15 is the best choice. Calculus may go better when you know some trigonometry and analytic geometry--and maybe patch a few gaps in your algebra.

(2) As you encounter things in math classes or independent reading that you don't understand, try to figure out if there are gaps in your background that may account for the difficulty and how you can go back and fill in the gaps.

(3) Because you're interested in uses of math in addition to theory, maybe look into aspects of physics, computation, statistics, and probability where math that interests you is used for various purposes.

(4) Think about the mechanics of solving problems: Here are a couple of suggestions to get you started. (a) Given the equation of a line and the coordinates of a point that is not on the line, can you compute the shortest distance from the point to the line? (b) Can you figure out the sum of this series? 1+1/2+1/4+1/8+⋯.1+1/2+1/4+1/8+⋯. (c) Given the equation of a parabola, can you figure out whether it crosses the x-axis? (d) What points in the plane satisfy |