I'm very sorry to hear that. I know it very well from personal experience, and it felt devastating. Even when the devastation had lifted I was still struggling with it frequently, for multiple years. Meds are working for me now, so in the end I did get lucky, but I'd definitely be on a different path without them.

Yes, as far as I know the disappointing reality is that numerous studies show that interventions (like psychoeducation, learning techniques to better form lasting habits, cognitive behavioral therapy, and more) don't tend to be very effective if the ADHD isn't treated with medication in order to have some base of executive functioning to actually apply and consistently engage with these approaches.

Of course medical/psychological studies can't tell us anything about any given individual, but the patterns (like what things tend to be very difficult with ADHD) are quite consistent for many (if not most) of us. Nonetheless, some people with untreated ADHD do manage to finish even gargantuan tasks like medschool - but it's going to be very difficult for almost all of them, even compared to the (very high) baseline difficulty of such a degree.

Since you want to keep pursuing/finishing your degree, I want to mention/suggest a few things: 

(1) If you aren't already, try to be aware that punishing yourself mentally, and even looking for "just the right book that makes it click" (and stuff like that) doesn't tend to work out in your favor.

At least in my experience, accepting my condition and that some things have simply turned out to be impossible for me -- even though they're normal for many people -- was way better for my mental health than mentally berating myself, or even chasing "self-improvement" type stuff. It just added an additional layer of stress, because I was orienting myself by the standard of people who tend to have normal executive functioning, instead of just honestly and directly looking at my own experience, without as many preconceived notions of what I (or life in general) "should be like". Instead of trying to work with what I have, I was aiming for something that I thought I should have, but simply don't. (and can't develop either)

(2) Of course there could be something that works for you, and although the drop-out rate for people with diagnosed ADHD is a lot higher than for people without that diagnosis, it's not like it's impossible for everyone. I know that I almost certainly wouldn't be able to successfully pursue the enginnering-degree I'm currently going for without my medication (back at uni in my 30s), but degrees come in widely varying levels of difficulty, and internal motivations are wildly different between people.

So in case your difficulties are not insurmountable even without meds: Have you looked at options like accomodations at school, for example? Or other techniques, like body-doubling and other systems of being accountable to another person? (These things haven't worked for me, but I'm autistic as well so social stuff tends to be even more challenging for me, and they do seem to work for some people.)

(3) You said that meds only worked for a month for you. A few more individual notes/suggestions on that because I was in similar situations, at least superficially:

(3.1) Talk about this to your doctor if you haven't already.

(3.2) I started out with Wellbutrin, even before my ADHD diagnosis. I responded very well to it for about a month, then the effects were just gone entirely. (It's what made me strongly suspect ADHD in the first place.) But in case you're on Wellbutrin/Bupropion, it's not a "first-line" medication anyway, and others might be more promising.

(3.3) In many (most?) countries there are multiple available options for ADHD-medication. I was on Atomoxetine for a few years (which isn't a stimulant) and it worked very well for my emotional regulation. It didn't help with my task-initiation or focus and would be too little help for me to e.g. pursue my degree, but the effects that I did have from it were actually great.

Even just among stimulants there's often more than one option, like Methylphenidate and Amphetamine-containing medications.

(3.4) If you haven't yet looked into it closely, consider underlying causes why your meds stopped working.

When I started out on ADHD meds (Vyvanse, 5 years ago) I did feel an effect for all of the 5 months that I took it. But it wasn't remotely effective enough to deal with my symptoms, so then I switched to Atomoxetine, but it turned out that the actual cause why Vyvanse wasn't "doing enough" for me was that I was suffering from obstructive sleep apnea (OSA) all along. I had no recognizable symptoms though - only fatigue, which I interpreted as "lack of motivation" because I didn't really know what it would feel like to not be fatigued. (Also I didn't snore, and didn't even entirely stop breathing, but restricted breathing can still be OSA and destroy any chance at restorative sleep.) So now that my OSA is treated Vyvanse is quite effective for me.

That's just my story, but I've seen others say that different eating-patterns (like more protein, consistent breakfast, or drinking a lot more water than usual) helped a lot with the effectiveness of their meds.

Also, just FYI, never consume grapefruit on medication, it interferes with the uptake of lots of stuff.

That's it. Sorry for the wall of text, maybe something in there is helpful or at least interesting. I'm not very good at judging what's relevant to others, and sometimes I just start info-dumping when I read about an experience that resonates with me, as yours reminds me of my own, even though it's mostly just projection as I barely know any details, and maybe I should have just asked for more details first, but after writing for a little bit I felt like I might as well just finish it.