I bet your parents already know something is up so knowing what it is will help them understand what is going on with you better. You might even find out that it runs in the family as I did when I told my mother that I had bipolar. But when I told her that a neurologist didn't know why I had these funny spells where I would be totally spaced out and feel very strange so he diagnosed with ADD as I read several book at the same time, my mother burst out laughing as did my ex-husband. They both knew how hard driven task oriented I'd always been so they knew that diagnosis was nothing but foolishness.

Parents know their children, and knowing what's going on might help your relationship in the long run. Give them a chance. You might need them later in life so don't blow them off.