I relate to you being able to sail through school. I never put in any effort when it came to school until I got into the later years of high school at a rigorous private school. I realized that I was falling behind quickly and was having trouble focusing during lectures and longer classes. I happened to be seeing a therapist for anxiety at the time who agreed with me about the possibility of ADHD.

I think that if you are curious, you should see if there is a school psychologist or disability counselor on campus. Many schools don't do ADHD evaluations anymore but they might be able to give you a preliminary quiz type thing and refer you to a good psychiatrist/psychologist. That person can do a full evaluation and give you a concrete answer. I don't think you should worry about disclosing that you might have ADHD until you know for sure (unless you need to tell your parents for financial reasons). And when/if you do decide to tell them, I don't think it will be as bad as you think. Most parents just want the best for their kids. If you explain to them that the diagnosis is a good thing and assure them that you are taking steps into treating your symptoms so that you can better succeed in school, they will most likely adjust to the idea.