18 years old...2 months late period?

I'm 18, and I've had my period for 6 years. The longest it's been late is 9 months and I was 14. The longest after that is usually just a month, but it's been almost 2 now. Last I started was the 29th and I'll usually start PMSing the day I started last month f that makes sense, but I haven't had one symptoms yet. I have had bad hot flashes though the past couple days. I'm not pregnant, I'm a virgin. Usually my first PMS symptom is my boobs are so sore and tender, but I've got nothing. Any ideas?? Hormonal changes??