I bled really heavily at 5 weeks and heavier again at 6 weeks, both times had bright red blood, and I passed a number of clots (sorry if TMI) at 6 weeks. Both times I had an internal scan which showed my baby was fine. At the 6 week scan they found a blood clot in my uterus and I had brown discharge from 6 weeks till 11 weeks. Haven't had any bleeding since then, and when I spoke to my midwife about it she said brown blood is old blood. The hospital also told me at 6 weeks, they would expect me to be in quite a lot of pain if I was losing the baby.
Am now 22 weeks and baby is fine.
Hope this works out for you, if I was you I'd get myself to the EPU and get a scan tomorrow if only to put your mind at rest.
xxx