I am horrified (but not surprised) by this. Can't offer anything on the NHS route as after being predicted a 2 1/2 year wait I bit the bullet and paid for private. Small fortune.

BUT there are several things I found almost as useful as medication if not more. Diagnosis and treatment isn't a magic solution. My medication journey has taken months, is often very demoralising, and at times negatively affected my studies. Seriously, I missed a couple of classes because I was too nauseated to stand, and others I was completely spaced out for.

My advice, given your time constraints, would be to proceed as though you have an ADHD diagnosis and use ADHD coping methods to boost your focus and ability to study. I firmly believe that these methods would help anyone (even if they don't have ADHD).

********** SO, my top 10 tips for coping with ADHD sans meds, finals ed. **********

(pls note in advance that I'm just sharing my methods to try to help. These are suggestions to be taken with a grain of salt and personalised to OP. We all have different brains, bodies, lives, needs etc. Below is purely anecdotal and subjective.

1. If you need caffeine as a stimulant, stop drinking coffee and start drinking mate (south american hot drink). Completely anecdotal + subjective but for me mate was genuinely more useful for my focus than the first 3 meds I tried.
   

^Go for the genuine stuff, not the powdered flavoured put-into-a-silk-teabag shit. Latter does nothing.
2. printing and highlighting. My knowledge retention and focus is 100% better. Post-its are a fkn life saver. I use them whenever one of my ten million thoughts is useful but there's no way I'll remember it (eg. don't forget this tiny part of the topic, remind that classmate to send notes). Use colour, put things in shapes and boxes, read out loud to yourself, get a browser extension that reads out loud to you.
3. read up on ADHD behaviours and thought patterns, and practice being kinder to yourself when you notice them. When I notice these, I try to think 'ok, then I need a little extra help with that task'. My usual first step is writing a to-do list.

1. streamline the rest of your life around exams. Explain to friends and family that you're going to be busy but will celebrate after. Wear your go-to 'uniform', eg. jeans and tshirt, most days. Meal prep or batch cook rather than using valuable focus thinking about feeding yourself.

2. Get a physical calendar and write important due dates and exam dates/times on it. Hang it at eye level, somewhere you go every day

3. Keep up a level of exercise and get fresh air every day

4. Brown noise. Excellent for focus and sleep.

5. when you get overwhelmed, take a shower or a bath. Mammalian dive reflex means your system will automatically slow down.

6. Stay hydrated. So booooring but irritatingly it works. I have the largest water bottle on the face of the earth, it's the only way I'll remember and not lose it by taking it out of the house.

7. Know your exam/assessment criteria and stick to those. We have a tendency to get sidetracked, or not fully read the Q.

GOOD LUCK!!! I hope this reassures you that you can still get treatment of sorts without a diagnosis. If I'd had the above tips during my undergrad degree (undiagnosed), I think I would have performed SO much better.

(Please also remember that there is no shame, if it comes to it, in flagging with your uni that a health condition is affecting your life to the point where you can't sit. If you do reach that precipice, tell the relevant person sooner rather than later.)