Implantation or period?

I am currently 8DPO and I’ve been experiencing dull cramps in my lower abdomen and a more noticeable aching in my lower back! My boobs are not very tender but I have veins that seem to be really prominent and they seem to look a lot bigger than usual!Could this be implantation? Or period? I wondered weather it’s possible to experience period symptoms when I’m period isn’t due for another week? X