Hi Exactly 27days Ago I Had Sex With My Bf..but

Hi
exactly 27days ago I had sex with my bf..but there was no erection of penis into me..though d guy had ejaculated..
In this 27days I had my period too at the right time..period generally delays by two days.
What I found today was a dead sperm .
does it mean I'm pregnant?
Please help me..tell me any medicine which I can take..I do not want to be pregnant.
Please help me.