Girls ONLY !!! I'm STILL having problems with my period. ( Please read details.)?

Im 15 Ive had my period since I was 11. I never had a problem till like two months ago. It stopped coming, and I know FOR SURE I'm definitely not pregnant. I'm scared that smiting is wrong but I don;t want to go to a gynecologist, the first month this happened I definitely believed it was because it was stress im still somewhat stressed out but not as much as I was then. Please help me find an answer to my problems. And PS me and my BF have never had before.