If you are only 8 DPO it is highly likely that you wouldn't get a dark BFP this early unless you used an ultra early test so I'd say that it could very well be the start of one. Many factors, like even drinking too much the day before, could affect the reading when testing that early. I can never get a BFP until around 10/11 DPO and even then it was faint so you've still got some time. Fx that it gets darker for you!