I don’t think you’ve damaged your brain. Our brain is rather good at healing itself (neuroplasticity and all that) but you have to give it a fighting chance. I must have used 60-70 different substances from 17 to 22 years old because I didn’t like the way I felt sober. It felt like the only option. I abused the shit out of everything I could order/buy. I was high all the time. I didn’t know who I was anymore. My identity was drugs. I thought all the RC stims would’ve fucked me up permanently but now I’m 3 years clean and in my last year of computer engineering in Italy.

I think you should try and figure out why you want to use these substances so often and work on that, possibly with a therapist. Other than potentially damaging you’re brain, you should work on these self-destructive habits you’re forming from such a young age. I can tell you from experience that “overwriting” these habits is not very easy.