Well, first of all, your struggles are real and I'm sorry to hear you're going through that. Normies don't understand but school/college can be very tough for some, especially if you have ADHD-like tendencies, it can feel like going to war.
Unfortunately, ADHD medicine doesn't seem like a long-term solution. I mean, it could work if it were cheap, but I understand very well how expensive medicine can be, that's one of the reasons I'm not on anything (other than the fact that this shithole country LITERALLY doesn't have any in stock, it's even illegal iirc god damn shithole). Anyway, since that's not an option, tbh all that's left is the hard road. And I don't really have the right to tell anybody to take the hard road since I've avoided it my whole life. I just took the path of least resistance, lay depressed in bed for years and just "studied" meme degrees that aren't worth shit.
Anyway, while I don't have the right to give advice, I do have an idea on what you should do. The big problem is mustering the energy and motivation, of course. People don't understand how hard just getting out of bed can be, much less actually doing something that requires a fundamental shift in the way you do things. My advice boils down to what NOT to do, really. That's all I can give you. Don't rot. And by that I mean don't stay all day in front of your PC all by yourself. That's what I did for years and years and tbh it does more damage to your life than you can think. Idc if you just go outside and take walks all day or ride a bike or something, as long as you're not rotting in front of your PC you're doing well. Also, don't replace your needs for medicine with alcohol. I fucked my life up beyond measure with alcohol, take my word for it, never ever drink, especially alone. Don't do it.
Well, my advice was useless as usual, but that's all I can give you really. I still have trouble studying, I myself have ADD + depression and others. Over the last few years I stopped studying altogether, and cause it was a meme degree I managed to pull through but the degree is so useless that my lazy ADD ass was able to not study and somehow make it. It's a sickness, really, I wasn't able to study even for 10 minutes, it felt like death to study at all. All I could do was rot in bed with my laptop. So my point is to again, never rot.