Confused?

I’ve been on my current method of birth control for 9 months, it’s the pill. A few weeks ago, I noticed I was a day behind on my pills but couldn’t remember a night that I didn’t take one. I set an alarm on my phone and take it at the exact same time every day. Anyway, now I’m on the placebo week, and my period usually starts around the 2nd day of the placebo pills, and it’s still not here and it’s day 5. I took a pregnancy test a few days ago and it had a faint line, but when I took one yesterday it was negative. So now I’m just wondering if it’s normal to skip a period every now and then? I mean, I’m pretty sure my body is used to this pill and this is the first month it’s been off. Also, I’ve had zero signs of PMS like I normally do. No sore boobs, no headaches, just some very mild cramping. Please reassure my paranoid mind!