I also deal with ADHD and I know all about repetitive thoughts. Whatās important to remember, though, that itās just your brain misbehaving, itās not a clear view of reality. Itās not your conscience or planning thatās telling you āimagine if you attended Harvardā, itās that part of your brain that is messed up because of ADHD. There are different methods and tricks to stop those repetitive loops in your brain, and that is something that you should look up and try.
To be absolutely honest - the shame is entirely theirs, not yours.
It was the responsibility of your parents to make sure that your ADHD was diagnosed and treated, and they dropped the ball. You have done the best that you could do under the circumstances and your best included getting a well-paying job.
If you needed glasses and your parents refused to get you diagnosed with myopia and refused to get you glasses, would you feel ashamed of not doing well in school? That is the same thing.
They may not be entirely at fault - they may have been too busy working, not been familiar with the entire concept or AHDHD, etc. However, that just means that their neglect was because of ignorance, not because of malice, but it was still their neglect, and you are where you are because of their failure.
You do not owe it to your parents to attend a prestigious colleges, or even try to attend a prestigious college. You owe it to yourself to find the best way to make sure that you will have a secure financial future. Trying to find a way to attend an āeliteā college will not help you secure your financial future, and may actually endanger it.
I will repeat: You. Have. Not. Failed.
Now go and start planning how you will do those six additional courses to secure your transfer to GMU!
Also - everything that @Lindagaf wrote.