Doctors are unbelievably rude sometimes! Just ignore him!
I don't want to scare you, but there is always a chance you could be experiencing a chemical. I had one in October, got my BFP and started bleeding the next day (the day that AF was due). It started brown and then turned red with clots, and over the next couple of days my tests faded until eventually there was no line at all. I did have terrible back ache and cramping with it though.
Have you had any pain or cramping? If not then I would remain positive and just keep testing every morning to see if there are any changes in the lines. At this moment in time I wouldn't worry too much, like I said bleeding can be quite common in the early stages so it could well be nothing to worry about.