Uterus throbbing/cramping normal?

afsalinas

I know that I'm being totally paranoid and it's my stupid IF brain, but I can't help it.

I just turned 16 weeks.  For the past couple of days I have had a dull throbbing feeling that I'm pretty sure is my uterus.  It almost feels like when you're about to get your period.  It's not sharp pain, its a little hard to describe... more like achey, and throbbing and it will come and then go quickly.  It's not consistent.

I still have about 2 weeks until my A/S scan and I'm feeling really nervous about waiting until then to make sure the baby is okay on an ultrasound.

Please tell me this is normal.