If its really bad, to where you double over in pain, that means something is wrong. I miscarried at 5 weeks a few months ago, but didnt know until I was 10 weeks. I didnt have any bleeding so didn't think I was miscarrying. Definately see a doctor. Hope your not experiencing one though, goodluck.
However...implantation can take up to 10-13 days to complete and you can test positive after the 1st day of the implantation process starts due to hormonal changes...
Implantation has already occurred, otherwise she wouldn't have a positive test. If the pain is severe, you need to get it looked at by a doctor or at the ER.
That happened to me too a few days ago. I'm six weeks now.
Very possibly implantation cramps...my back hurt sooooo bad (with no bleeding) i thought i was miscarrying and i was around 5 weeks...it lasted like 2 days...im almost 14 weeks now :)
Same here and im only 3 weeks!