I had this at 6 weeks, and the midwife told me that it is very common to have implantation spotting during early pregnancy, particularly between 6-7 weeks. I was so worried, but near enough every women I spoke to after had some kind of spotting during their pregnancies. Try to relax. I phoned the EPU after my spotting, and they said, if it has stopped and there is no pain, to just forget about it, but if it continued, or I had pain, to get in touch with my midwife.
Let me know how you get on! Good luck, hon xxxx