Implantation bleeding or old blood

Implantation bleeding or old blood? Sorry ladies for d grossness I’m jus really worried. My boobs are tender and for the last 2 days or so I’ve been bloated. I took postinor 2 after having sex. I had sex on the 25/26 May and I took the pill on the 28. My next period is due around Friday or Saturday coming. Could I be pregnant or this is just effects of the pill? Any thoughts?