my parents won't let me grow up

Every time an opportunity comes up for me to go to a party (just close friends) where everyone sleeps over, my parents always say no. I'm 18 now and they still treat me like I'm 14. Some ppl think I don't like them because I never go out to social gatherings when I'm reality it's because I'm never allowed to go. I'm sick of it. And to top it off, my mom just realized that my friend who was thinking of hosting the after prom party, lives slightly outta town (30 min away). Like it's prom. I'm not gonna let her call the shots for MY PROM. I'm so pissed rn
Any advice?