“I have thought for years that I have ADHD. I took a stimulant and was so relaxed and calm, I went to sleep right away. Does this mean I have ADHD?”
ADHD is a serious medical disorder. It should be diagnosed and treated by a physician who knows of this disorder. There are many reasons why an adult, especially one with the multiple problems you describe about yourself, might respond by becoming calm and relaxed. See a professional and address your problem more seriously.