Replying to US healthcare privacy question

I'm 18 years old and a senior in high school and I'm pretty positive that i have ADD or ADHD. I just cannot focus on anything, it's not because I'm lazy. I don't want this to turn into a "whether or not I have ADD' thread. My question is, I'm on my parents healthcare and I've heard my dad say ADD doesn't exist, so I'd like to keep it hidden. Even though I'm on their healthcare is there anyway they could find out that I went to the doctors to get tested for it?

thanks and +k for legit answers