I don't think it's implantation bleeding, because you only get a positive test result after implantation already took place. The bleeding is either because you had a miscarriage (this happened to me) or there is something going on with your pregnancy. You should definitely see you OB so they can see what's happening. In my case, I took another pregnancy test a day before the bleeding began--I just wanted to enjoy seeing another positive result. But it wasn't positive that time. I had been having horrible cramps (felt like bad gas pains), so I realized that I must have miscarried. The bleeding came the next day. My OB still wanted to see me, just to make sure everything had left my uterus so there would be no infections.
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