PAP SMEARS?

Going for my first exam soon. I finally built up the courage to ask my mom to make me an appointment since lately I’ve been smelling bad down there and i am sexually active. I’ve been wanting to get on the period for a while but my parents haven’t let me. My mom said i might as well get on it while I’m there so that’s good. But my mom doesn’t know I’m sexually active and when i go to the doctor i don’t want my mom to go in with me. How do i tell her i wanna be alone? And how is a Pap smear. What will they do first. I’m really scared. I’m 17.