No doubt you have ADD, from your symptoms and having been diagnosed.
I was a gifted student in school, before ADHD was even a term.  I did well in high school until there were courses that required sustained study built upon retaining progressively more difficult learning, such as calculus.
A counselor who thinks that there are not brilliant people with ADHD is sadly misinformed. Your psychologist does not know that people with ADHD are capable of sustained attention in some tasks that interest them (called “hyperfocusing”).  It takes work and ignoring other stimuli to do that, and while doing it you may not be able to hear or process what someone is saying to you as well as a normal person.  You may sometimes be told “you weren’t really listening to me” because you wanted to listen but also had other thoughts on your mind.
One thing you can probably do to help counselors understand is look up some tests online for tasks in which you can easily demonstrate difficulties, or carry a diagnosis report.
You will have to work at getting the help you need.  In the work world there are rarely managers or employers that are supportive.  Some medical schools have had successful ADHD students, and you should probably choose a program at a school where ahead of time you know that they have a great support program or that people in your field with ADHD have done well there.
Good luck, and I would be glad to give more information if you need it.  Some of the books on ADHD have good sections regarding how it can hurt your self esteem, and things you can do in that regard.  Start dealing with that now, so your aspirations don’t get squashed!
Dan

I feel your pain! I am a junior with a 3.95…I kept getting told I couldn’t possibly have ADD/ADHD because I have good grades. I have not gotten special accommodations because I am usually the first one out of tests…I have to get all the info out ASAP, vs needing more time because of distraction.
I agree with Dan…hyperfocus can account for the good grades in spite of the ADHD. I am recently diagnosed myself so I don’t have much advice to offer except that you know yourself best. I am not encouraging you to be a doctor hater and think people who say you don’t have it are just stupid…but you DO know yourself best and it is absolutely worth the trouble it causes to find someone who will listen to you.

Geez, I am getting in on this months later. I too am recently diagnosed except I am 62. I did very well in college where we are measured on performance (3.9GPA). And I have done well in other circumstances where there is a measuring stick. And yet I have always known something is wrong with me. I am just figuring out how ADD is/has affected me but I was struck by your statement ? ¡Ènothing is seriously wrong with me except my self hatred¡É -and your feeling of being held back.
These thoughts are very serious and are harmful to you in ways that you may not imagine at this point in your life. As I said I am 62. Those thoughts and other similar thinking plagued me and defined me for many years. I started shedding that type of thinking only about 10 years ago. I am hoping you will shed those thoughts now. When you are aware of those thoughts replace them immediately with positive thoughts which, by the way, turn out to be much more accurate of who you are and what will come your way.
The opinion of others especially those just looking at your performance is just that ? an opinion. Take whatever accommodations you are offered with joy. You don¡Çt really know how that calc test would have turned out had you not had the extra time. (Mine was a B. Would it have been an A if I had more time? I don¡Çt know.)
Good luck to you and congratulations on your achievements.

ADHD in an of itself is not a learning disability.  We know that its not uncommon for a child/adult to have a co-morbidity such as a learning disability along with ADHD.  I have ADHD and I did well in school; Of course I waited to the last minute to do my assignments, but I always managed to complete my assignements and score above average grades.  My undergrad senior year was really the first time I can say that my ADHD caused me to struggle and drastically under perform.  My classes were very unstructured and required a great deal of self-regulation, motivation, and task/time mgt. 

In terms of you needing to convince others (and yourself) that you are ADHD—why don’t you just go to a reputable psychiatrist and have him/her conduct a full assessment?  You said you were diagnosed twice; Is there any reason you would have doubt and question the accuracy of the outcome? 

I think you might find the information on this page really helpful. 
http://www.help4adhd.org/en/treatment/guides/WWK9

i was diagnosed with adhd whilst dooing my masters in counselling and the ripe age of 46. after the initial shock and denial which for me lasted a year i began to get understanding of what the condition entails. this was 7 years ago.
rather than seeing i have a deficit disorder i realise that having adhd is a different kind of normal with benifits and liablities and that with a good understanding of the conditioni with my wife deal with this different normal sucessfully.
The knowledge of having adhd has explained so many of my behaviours and now rather that being the problem we can externalise problems to adhd and work to deminish the negitive affects and enhanse our relationship.
Finding out as much about adhd has been the single most benificial decision i have done.
Hopefully this may be helpful to you