I am sorry to hear that. I have had 2 miscarriages and both times I had been spotting brown blood. It was devastating for me to find out that both pregnancies were over before the heart beat was found.
With this pregnancy I spotted on and off with brown blood up until 8 weeks. But with my last pregnancy I spotted brown blood for only two days then turned into a red heavy bleeding and later that night I miscarried. So its pretty hard to tell :/ but since its still brown then you may be okay. Only way to know is a ultrasound or blood test. Good luck.hun