First ultrasound showed healthy fetus, second ultrasound no fetus or heartbeat. did i have a miscarriage?

Exact answer needs .: Details and review of the images. Given what you describe, and assuming no mistake with the first ultrasound (meaning there was an embryo), then the lack of a viable embryo/fetus would mean a miscarriage during the interval. Please discuss with your ob/gyn. A blood test of the pregnancy hormone (HCG) can be performed twice a couple of days apart - if decreasing, would confirm pregnancy loss.