I'm 18 and not ready for a baby

my last period was May 22, 2015 and it ended May 28, 2015. I recently had unprotected sex June 1st around 2:00 pm (we used the withdrawal method). I started to feel scared about it so I purchased plan b June 3rd at 10:00 am. My several fertility calendars said that ovulation would occur June 5th, 2015 and my fertility window would end on the 7th. Today is the 8th and I'm experiencing brown discharge (it's kind of stretchy and fades out when I wipe). I know it is too soon to tell , but can anyone tell me if this is implantation or is it something that happens after ovulation?