I'm 27, and I've recently been diagnosed with ADHD a few months ago. When I first met with my psychiatrist I told them that I suspect I might have ADHD, and I told them why. There was a few appointments. I had to go through several evaluations where I answered a bunch of questions and they watched me closely when I was in. Then they interviewed my family to ask about my history and how I acted growing up, and then they started me on stimulant treatment. All in all it took me two months before they started medicating me.

Just make sure you're seeing the right doctor for the right treatment. As far as I understand, a therapist can help you with cope with ADHD by helping you find ways to form habits to overcome your symptoms. a psychiatrist will help diagnose you officially and work with you to find a medication to help mitigate your symptoms.

For me they put me on Adderall and it has been completely life changing, but I've been told my case is pretty severe. (For context, my Dr. doesn't like to treat people with stimulants first, and usually tries to treat for depression or other conditions that have symptom overlap with ADHD first, but he moved me to stimulants after interviewing my family.)

As amazing as treatment has been so far though, as they've been slowly increasing my dosage, the side effects are a bit rough, the medication wears off later in the day causing a crash - especially when I first started the come down was rough, and after about 3 weeks started to lose effectiveness, and no matter how much they've increased my dose it has not been as effective as it was in those first three weeks. (Tolerance seems to be building fast for me :< )