Help?

Okay so I was supposed to start my period Friday, I was waiting and waiting, nothing Saturday or Sunday, last night I started to feel sick and I puked, this morning I started bleeding, however the only times I’ve been late is when I was pregnant, I’ve never been late otherwise, I’m still feeling sick and i felt so dizzy this morning, can anyone tell me why? I was kinda convinced I was pregnant until I woke up today, it’s not really really heavy however it’s quite painful.