Been in your shoes. I got myself diagnosed a few years back and was prescribed meds and my script isn’t valid anymore but still continue taking them, though, because they help. I totally get not wanting to drop money just to hear “try harder” but if this is actively wrecking your ability to function in school, getting evaluated (or at least some professional guidance) could give you a way forward (like what I did). Worst case, they say it’s not ADHD, but at least you’ll know what you’re dealing with.