Implantation bleeding?

I was wondering if its possible to get a bfp during implantation bleeding, or if its just a waste of a test. I just started spotting today, its a week before I'd normally start. Ive also have had sore nipples, heightened sense of smell, and some nausea. Which isnt normal. I dont want to get my hopes up, maybe af is just coming sooner. What do you think!?