Could this be implantation?

Hello Everyone! I have a question on implantation bleeding if you wouldn’t mind enlightening me. I had sex on Aug 7 & 16 , my period was technically supposed to start on Aug 26 and i am regular every 30 days but it did not start. I’m thinking i may have ovulated later. Also, on Aug 27 & 28 i had brown spotting the size of dime . I tested today and the test was negative .. could i still be pregnant? I also do not track my ovulation so I don’t know exactly when i ovulated.

Please enlighten me if you can. Thank you! 💗