My fiancée had a miscarriage 3 weeks ago, and has been having bad stomach craps ever since, I ve tried to get her to go see a doctor but with no success. She took a pregnancy test 2days ago and it came out positive, the problem is we haven t had intercourse until 3days ago. Can you give me an answer to this?

Go to a Doctor... She could have been pregnant with twins.. lost one kept one, she really should be under a doctors care right now
... I am not a medical professional and I can't give proper advice about anything except that she should been seen by a professional.