Bleeding after sex or implantation bleeding?

After sex, I noticed I had a brown and pinkish looking discharge. I never bleed during sex, not even my first time. I'm wondering because we are ttc if I maybe have implantation bleeding?? It's spotted in my underwear as well but now I am very dry down there and have no discharge whatsoever. We had sex last about 7-8 days ago so it is in the time frame for implantation and I'm on day 21 of my cycle. We didn't have sex rougher than usual so could it be more likely from sex or implantation bleeding?