OP, it’s best to tell your parents, and tell them that you want to see a psychologist for it.
Your insurance may be able to defray the cost.
Your parents may be outwardly calm, or they may be openly upset.
If they’re calm, it’s because they’re already suspicious that something’s up with you, and they may have practice dealing with mental issues in the past.
And if they do get upset? It’s because they love you and are worried about you, and are probably wondering what went wrong, either with themselves or you or both. And that’s perfectly normal, and you need to give them the space for their sadness, just like you want space for your sadness.
But insist to them that you want counseling.
Yes, things are going to be weird for awhile, but so what? Are things so great now?
The most important thing is you on the road to recovery.
God bless, OP