Your husband getting defensive (thinking you're making him sound dumb) and trying to almost bar you from getting tested for a diagnosis sounds quite like a symptom of ADHD he is experiencing, haha. Total self-confidence and stubbornness over an idea/"fact" is huge, as is continuing to press that point even if mentally they've realized they are, in fact, wrong.

Definitely pursue getting a test/check up if you are concerned. If you do have ADHD, having secondary evidence that a doctor thinks you have it too will likely make him lighten up a bit or be completely enlightened.