pink and brown discharge early scan results

so for the past 2 days I've been getting brown in my underwear which I assume its old blood and last night when I wiped it was pink, from my last period I should be around 6 weeks and 1 day, this afternoon we went for a scan and all is good we seen and heard the heart beat although the lady that did the scan said I'm only showing at around 5 weeks, and the heart rate was only at 100, so very low... hopefully it picks up as I won't have another scan now until I'm 12 weeks so hoping we get there