First doctors appointment for mental health since elementary

I’m 20 about to be 21 in 3 months. The last time I went to my doctor for mental health I was in 5th or 6th grade. Tomorrow I have a physical with a new doctor which they’ll take a pee test. I definitely have thc in my system as I smoked all weekend not thinking about it because I got my dates mixed up. I don’t have time to go to a smoke shop to get the detox drink and I need to get probably diagnosed and get help. Will they deny me help because of this ?