Why Is The Period Delayed?

Hi, I'm 16 years old and I'm still a virgin, never had sex in my life. I just got back from vacation and i wasn't having a steady sleeping cycle during it. I had hard times falling asleep at night because of general discomfort from the room and beds. My family and I drove for about 23 hours in a car to get there and 23 hours to get back. During my vacation, I was active with swimming and walking alot. I wasn't eatting very healthy, most food was fried. I usually get my period around the end of the month (24, 25, 26) and it last until the 1st or 2nd of the next month. I just got back home from my vacation yesterday. It's the 27 of the month and my period is about 1-2 days late. I've had my period for about 5 years now so it's pretty steady. I'm freaking out and i have no idea what's going on. I know i'm not pregnant but i'm still worrying and freaking out. Can you tell me what's going on?