Implantation or no?

A couple weeks ago my boyfriend & I had unprotected sex (around the 29-30th I think). It didn't take long at all, as he goes quickly without a condom. So literally like 3-5 minutes, maybe. He pulled out, way ahead of time before finishing.

I take the pill every nights and haven't missed one. my last period was the 24th of august. All has been normal with my body since.

On Wednesday night (9/6), he fingered me, and was kind of rough. Thursday (9/7) afternoon I noticed a slight amount of brown discharge but didn't think much of it. Today (9/8) I woke up fine, but by mid morning noticed some light pink discharge. I put in a tampon before work & just got off work to check it, so find the tampon covered lightly in light pink. I've also had diarrhea today, but was leaning towards some cake I ate last night being the cause (I don't eat sweets much).

Should I be worried about implantation bleeding or could this be from the rough action on Wednesday?