Guys could this be pregnancy or is my body tricking me?

So my last period was on the 12th July, I had unprotected sex on the 24th July, and I started bleeding (very very lightly more like discharge) on the 31st July. (7 days after unprotected sex) my period is not due for over another week and i have never been early in my life. My boobs feel so heavy and look veiny, and I have been feeling sick and really hot. I wouldn't say I was still bleeding because I do not need a pad but my discharge is brown. Could this be implantation bleeding although it's almost lasted 4 days?