Vanessa, keep us updated.
My doctor told me that if I feel more severe menstrual-like cramping to call him and get in. I am high risk, though, so they don't want to take chances. I have been experiencing mild menstrual-like cramping, which is most likely ligament stretching but if it does get more severe I will be going in for an examination.
You do seem to have quite the big baby already, so perhaps it's only that. My goodness, I can't believe your baby is measuring 6 pounds. Even if the ultrasound is a couple of pounds off, the baby is still measuring big!! A part of me believes the ultrasound maybe close to accurate considering you were a big 12 pound baby. My thoughts go out to you!!! Let us know how you feel in a day or two.