Late period?

So my menstrual cycle is normally regular, and I’ve never had a serious problem with it before. I’m not on any medications or birth control or anything. I haven’t had sex since Jan 2nd (my boyfriend and I are long distance, it’s the day before he left)...so I’m confused because I’m a week late on my period. This has never happened before, and I’m confused. My boobs have been hurting for quite a few days, I’ve had some mood swings, and I’m pretty sure I ovulated...does anyone know what could be going on?