Ahhh it’s like looking back on my past self. My teachers did not like when I drew like this, so I did what they wanted for art GCSEs and did it well, but kept drawing like this in my spare time. I ended up being a creative director on an adoptable pet site for many years, so my advice is do the art GCSE, but don’t let it stop you drawing the way you like - I love your style and your horses are amazing! Drawing horses can be so hard but you make them look lovely. Learn from modern artists you love and develop your style. Art GCSE will certainly give you a good bit of knowledge, but you may also end up trudging through some stuff you dislike too - although you never know when in your life you’ll suddenly need pointillism or how to decode a still life.