Low Sitting

Colleen
So I've been having cramps and spotting off and on. Called doctor and got in for a sonogram. I'm actually measuring 6 weeks so I'll be having an October baby. Heart beat was there, and baby seems okay from what they see, but doctor said my uterus is sitting low? There's a chance I could miscarry with the spotting/cramps and that I'm sitting low. 
Had anyone else had this before?