Signs that i could be pregnant?

Hi, i'm new to this site but could really do with some advice. My last period was on the 2nd November, my cycle is normally 27 days. I had unprotected sex on the 8th, 10th then the 21st of November however on the 25th i had light cramping (thought AF was coming) then i noticed a tiny very light brown discharge when i wiped then on the 26th the discharge was darker but just tiny spots of it inside my knickers (just used a very thin liner) then i've had nothing since. My period is due today but i was wandering if it was implantation would that be from the 8th/10th or the 21st?? Thanks in advance for any advice you have...best wishes to you all x