Positive urine test, negative blood test, vaginal ultrasound showed sac but my doc is blowing it off. When I asked if I'm pregnant he just said NAH BUT YOU MAY HAVE SCAR TISSUE. I'm very confused. If I have a sac forming wouldn't that mean I'm pregnant or starting to be??

Is that a quote? If so then find yourself another doctor. Even if this turns out to negative I would still do it.

Bed side manners aside, there are a couple things that could be happening. One, the fetus was a little too small to be seen on the ultrasound so all that was seen was the gestational sac. It could also be a embryo that stop developing, Google blighted ovum, and your body is just waiting for the right time to flush it out. I would wait a little bit and get a second opinion.