Am I still pregnant? ? I'm scared that I have lost my baby.

Im 4 weeks pregnant. This is may 2nd pregnancy and I have no history of miscarriage. This is my 1st ultrasound since I have brown spotting for 12 days. Can anyone please enlighten me that this can be a false interpretation? The OB told me that retained product conception means that I have an incomplete miscarriage, or ectopic. Is that true? Or is it early to say? I feel so down ?