Pregnancy scare

Couple of weeks ago i had VERY drunk sex with a guy, and I’m not on a pill. The next morning he said we used a condom and he didn’t even orgasm because I passed out, and there was an open wrapper lying around, but I don’t trust him to have followed all the precautions. Now i did start bleeding on the day my period was supposed to start but usually my bleeding is heavy from the first day and this time it’s super light and looks more like implantation bleeding. Am I paranoid or should i get a test ASAP.

Ps. I’m mostly worried because all that happened during my fertile week.