runner and her period

Um wellllll I haven't had my period since August 24 and it's October 23 and still nothing. I'm 14 and a cross country runner we mainly run 5-6 days a week. We started August 10 ended September 23 and well I'm scared I never had sex because well I'm 14 and I don't want to do that yet. But I'm scared I might be pregnant. Somehow.  But Idk I'm scared I've been getting headaches maybe because I'm always on my phone or computer but idk. And SOMETIMES id get a lower stomach ache and well 2 months late makes me worried for some reason I don't want to be pregnant (I know how babies are made btw) I feel stressed because well I'm failing classes. And I have anxiety so I worry. And I'm paranoid of everything.   Help me idk what to do idk what's wrong