I am 6 wks pregnant and I have some blood during discharges. What should I do?

I had a +hpt at 4 wks and have been fine since then. This is my first pregnancy. Yesterday I went for a long shopping trip and walked a lot. This morning, I had dark red (not bright) blood during with a vaginal discharge. I do not think there was any tissue passed. Am I at risk for a miscarriage? What should I do to prevent this? Is there anything else I need to do? I do not have a family doctor and my prenatal appt. is not for two weeks.