sorry. this is gonna be really long!

so, here!

July 22 (23 days ago) I had unprotected sex (pullout method) and on August 7 (16 days after having sex) I woke up with blood in my panties, light blood but enough to stain my pajamas & my bed then it didnt come back after (i think its implantation bleed) then my period due is Aug 11 but its already Aug 14 now But I still dont have my period. I took a test today but its negative... I have sore breasts but just feels like the normal one like what I feel before.

I dont know whats wrong. i took a lot of vitamin C hoping for my period to please come.. is it possible that I am pregnant? should I test again? PLEASE help me.