I already know what I want to be but I also want to be in plays and stuff? What do I do?
Follow what you want to do! If your ideal profession/career is not in the arts/acting arena, go ahead and pursue that! There are TONS of opportunities (depending on where you live) to participate in community plays/musicals/live performances, etc.
In most cases, you'll still have to audition for the larger roles (especially if they're paid, some are not depending on the production), but many productions are filled with working adults where rehearsals take place during evenings and weekends in order to accommodate full time work schedules.
My dad was a cyber security professional by day, and musician as his passion. He was asked by a friend to help out for a local community play with music and a small role. That small role led to another small role in a difference performance, and he kept "trading up" to bigger and bigger arenas. He never did any acting professionally, but he had a blast and it was awesome seeing how many opportunities there are out there!
Take a look at where you plan on working/living/going to school after graduating, and google nearby acting troupes/theatres/auditions. Or, if you haven't decided where you'll be living yet after high school, start looking at potential places and see what their opportunities are to help make your decision!
You can definitely do both--granted, it will take time and might not be easy, but is very much achievable!
Bri recommends the following next steps:
Sounds like you've decided that the performing arts aren't your main focus, but that doesn't mean you can pursue a side passion while you're pursuing a career. Filling your free time with healthy and productive activities like theatre is a great way to keep a balanced healthy life. Make sure the company you work for doesn't expect crazy working hours so that you've got time to pursue your side passions!