Implantation bleeding or period?

I had sex around 2 weeks ago (unprotected, he pulled out). And I got my period 2 days late about 10 days after. I always get rather intense cramps and a heavy flow but this time was different I got no cramps and it’s a brownish color compared to the normal bright red, it’s definitely more than just spotting it’s about enough to fill up a pad. I got it for 4 days compared to my usual 6. I read up on implantation bleeding and it said it almost always comes before the period and mine was late not to mention it’s noted for spotting not a flow of any sort. I’ve been really stressed from exams lately and I know that can greatly affect your cycle do you think that could be the reasoning or could it actually be implantation bleeding? I’m fairly anxious and any feedback would be appreciated thanks!