It's your right
At 18, you are at the "age of consent" meaning you can see whomever you want and nobody is entitled to your information but you.
In many states, that number is 14 years old for psych or confidential issues. The fact you went, though is harder, since it often shows up on parents' eob's. You can pay cash, or get your own insurance
, but best to be honest and say you're going. It's your business why.