Great job posting up your situations here on beyondblue, more heads is better than one.
I had to repeat year 10 because I didn't study the first time around. After that I aced year 10, then year 11. Then didn't do enough study for year 12 and had to repeat that too! All to aim to getting in Uni and I did get into uni after 14 years study primary/secondary.
Didn't end there either, I dropped out of Science degree in second year, for a Maths degree which I dropped out of in third year. Worked for 5 years and came to dislike that too. Took yet another crack at Uni for Computer Science, and failed yet again! Like seriously!
Took me from 1991 to 2019 to achieve one actual degree, like as an academic outcome, a few Tafe Certificates along the way. Life went on in other areas, but academically I reckon I was way way way down. Fought my way through a Bachelor of Educational Studies, but covid arrived and no ceremony, just was posted a piece of shiny signed paper.
Ah well. Got there in the end hey.
Great idea with your headphones are they noise cancelling ones? cause those noise cancelling ones work really well, much better than just normal headphones. For the extremely quiet option go for a closed back circumaural noise cancelling headphone, make sure it's comfortable to wear for hours. However I used Bose QC20 noise cancelling earplugs which worked well. I've been told that Bose do even better ones too, but up there in price. Sennheiser also have a good reputation.
Can your parents afford something like those, or similar, to help your head space for study?
I'm a technology guy, so shiny new "toys" makes me feel better, and that might work for you too.
One thing I have learned is that it is possible to turn year 12 around with dedicated quality effort after the midyear failures.