Seeking advice on untreatable ADHD

I've (22M) been diagnosed with ADHD a few years ago and have been on many different ADHD medications (and antidepressants) since my diagnoses. These include both non-stimulant and stimulant medications, ranging from low to very high doses. Unfortunately, nothing I'm prescribed works. These symptoms severely impact my life; I feel like I'm constantly living at 40%.

Could it be something other than ADHD? I'm open to any advice anyone might have.