My period hasn't come for two months? Is this ok?

I'm not super concerned but I want to make sure.

I am a 15 year old girl who's had her period for almost a year. My period almost always comes late, by about a week or two, but I assumed it's because I haven't had it for very long and the cycle is still settling in.

But, my last period came October 5th and it hasn't come since, nor am I getting any PMS or signs that it is coming as of now. I am fairly skinny/small and school is relatively stressful (as it is for most high school students), but it never stopped it from coming in the past. I haven't been that stressed at all lately, and my weight has not dropped. Should I be concerned? I haven't gone so long without getting my period since I got it for the first time.

Again, it's almost been a year since I first got it.