Hello. A week ago I had an ultrasound, they said I was pregnant, somew…

Hello. A week ago I had an ultrasound, they said I was pregnant, somewhere between 3-4 weeks. Since the first days I have been having pain in my uterus and lower back, this became the reason to see a doctor. After a week the pain hasn't stopped, tolerable, but today I found light brown discharge, could it mean miscarriage? I wanted to go to the doctor today, but they work until noon, I postponed it for tomorrow.