I'm really sorry to hear about your miscarriage, T.. Not only is that a hard thing to go through, but it can make future pregnancies scarier. I have had similar bleeding to what you're describing all four times I've been pregnant (two sons, one early miscarriage, and I'm currently 20 weeks pregnant). The first time, it went for 3 or 4 days, I think, long enough for me to suspect it was just a light period, but I tested anyway, and sure enough I was pregnant. With my second son, I bled off and on for probably the first month, and it was the same this time. The difference was that when I did miscarry, the bleeding was definitely red and heavier. But I think that some women are just prone to bleeding early in pregnancy, and I've certainly heard of implantation bleeding.
I'm glad you're already on top of getting Hcg tests; that will give you better answers and hopefully ease your mind. Good luck, and I look forward to hearing what you find out!