My period is late and I'm freaking out?

Ok I already kind of asked this question, but I'm going to go a little more in depth.

I'm 18 years old, I've had my period since I was 12. It's normally regular, at the end of the month, but occasionally, it skips an entire month and starts at the beginning of the next month, which is fine.

When I was living at home, I was on a similar cycle with my mom and sister. I moved out and went to college in August, and my roommate has a different cycle than me so at first I thought maybe I was changing since I'm living with her.

My last period was two weeks early, and my most recent one should've been either this past week or within the next couple of days and it's still not here.

Here's why I'm stressed: Four times this month, I've shared a bed with a guy. I was always wearing shorts and a t-shirt, and he was always in shorts and didn't wear a shirt. We didn't have any sex whatsoever, but I'm paranoid and have a bad feeling he tried something while I slept?? But I'm a virgin so you would think I would've felt it, right?

I've also been sick for the past two weeks (so during my regular cycle), and I'm freaking out about the whole stupid pregnancy idea so I'm super stressed and I read where both of those can delay a period. I'm ALSO stressing because the guy I stayed with hasn't been talking to me lately, which makes me even more paranoid that he's keeping something from me.

So you tell me: Am I completely stupid for thinking I'm pregnant? Why do you think my period is late?