Chemical pregnancy???

I'm not 8 days late for AF, had implantation week before. I got a positive test on 21st for the first time, it was faint but there. I have had several positives but also negatives since. The positives aren't dark they are still faint. I have called the doctor and they said to just wait and see if I bleed if still same scenario in a few day to call early pregnancy unit. Surely so if they were already faint I would just be getting negatives by now? Anyone any advice