Insert the "who could have done this" meme with the FAA shooting interest in flying and # of pilots.
Note that 'undiagnosed ADHD' holds as much weight as me saying you have bad energies. There are many conditions that masquerade as ADHD to a layperson, including some purely psychological ones (they are no less real, but are very different from a neurodivergent brain and require very different treatment).
If you are otherwise a high functioning adult (can function in society, operate vehicles safely, etc), get your third class medical, which should be no problem. You have to disclose diagnosed conditions. Do a discovery flight and ask for an opinion from the flight instructor. If he thinks you are fit, go start your training and enjoy.
If, one day, you do get diagnosed (with ADHD or some other disqualifying condition) AND require medication, then it's a problem. If you don't need medication (because most if not all ADHD medications are prohibited), don't try to renew your third class medical (because, if you get denied, it's a big problem) and get advice about BasicMed. It has far less requirements; my understanding is, unless there's something strictly prohibited, if a doctor signs you up you are good to go.
You won't be able to fly commercial or faster than 250knots but I suspect you don't care.
Failing all the above, there's light sports aircraft and gliders(no medical requirements, you just need judge yourself to be capable and unlikely to be incapacitated) – although I am not sure you can operate them while taking meds; some professional advice required here.
Disclaimer 2: Obviously the above assumes that whatever you have does not impair you. This is just to get around FAA's antiquated view on mental health while complying with the law. The most important thing is to be safe. If you really can't due to health issues, then don't, even if a doctor says you are fine.
Otherwise, don't give up!
Can you explain this further?
Some conditions are uniformly disqualifying, for good reasons. But it results in a perverse situation where a regular person can choose to either get mental health care or fly, but not both.
https://www.faa.gov/pilot-mental-fitness
For me it's completely moot. I can't even have someone else fly me anymore--I have an (apparently untreatable) eustachian tube dysfunction.
...which is probably for the best given my bearish position on aviation.
Oh my sweet summer child.
If these things are that bad, those same people shoudn't be driving either. And this is probably true. However, if you applied these same restrictions to driving, people would absolutely go nuts on you.