4+4 and spotting

Just got my bfp a couple days ago...I tested on the day my period was due which was last Friday and it came back positive....I also tested 2 days later on Sunday and it was still positive and darker than Friday's test...However when I woke up this morning I had brown spots on my underwear and im really scared...im not cramping or anything but everything I've been reading on Google says miscarriage...anybody had something similar with a positive outcome?