RSD is one thing, but realizing you have a problem with it, as many males do, is not going to help you with your girlfriend. First, RSD should have helped you realize, perhaps, that your feelings of rejection are mostly imagined. The main test for a woman as to whether or not she wants you or believes you’re capable are simple: She is still there. You’ll know clearly when she has lost hope, because she will simply leave. Realizing the harm RSD does to you and others may help you feel better, but it won’t help your relationship in the long run.
This is becuase your main problem has nothing to do with RSD or ADHD, as evidenced by the familiar “fix” the issue mentality and your framing of her upset as over “minor” things. She also clearly has the same problem with you, as evidenced by her requesting you “figure it out” as if you can read her mind. You still don’t really understand “why” she does that. The issues there are very common, very basic male/female framing issues.
Fortunately there is something you can do to fix that, and it’s easy to find the solution(though harder to implement). There is a book called “women are from venus, men are from mars.” You can buy it, or find the PDF online. There are a thousand relationship psychology books out there, out of which i’ve read over 100 and found all but a few to be garbage. This one is the one you need. The writing is far from a masterpiece, but the concepts are all there. Don’t cliffnotes it or look at the summary, read it. When you read it you will feel just as big of an AHA! moment about your relationship as you did with the RSD article, only this time you will also know what to do about it and why it keeps happening (especially the big arguments over “little” things).
I finally found this particular book after many others to try and fix my first marriage. First I read it, then we both read it. And by following the simple suggestions in that book and one other, it did fix it, almost instantly, to the point I couldn’t believe how happy we both were. I was skeptical getting started, but once I realized that what I was doing would work reliably, I found it easy to keep going. Unfortunately, back in the days before I knew that things could be fixed some big mistakes were made, and when they were inevitably discovered that was the end. However, I married again almost immediately after, since I knew what to do for the next time, and we are still just as happy 5 years on. No big fights, no real problems except whatever life throws at us. I also used to think ADHD was the main culprit, but it isn’t. I haven’t changed, I’m still just as forgetful as always, I have less money and less stability than before, and I’ve not married an angel, but this time we both know how to deal with each other’s conflicting ideas of the opposite sex. Before the wedding, we both read the book, and I read it again every couple of years, just to check myself. I don’t even do everything it says now, (for example, I don’t do the letter thing for the most part, only once with my previous marriage, to excellent result) but even without doing every little thing, the newfound awareness still makes all the difference; you really won’t believe it.