Cervix funneling

Hi ladies. I’m 18 weeks pregnant and Last night I went into my OB for pelvic pressure. From the outside they said my cervix was hard and closed, but after an ultrasound they noticed that my cervix has shorted a bit from 3.7mm to 3.1 mm and I have a bit of funneling. My OB made a comment that I was a bit confused about, she had me push down as if I was giving birth and told me the funneling isn’t opening when I do that so she’s a lot less concerned. Have any of you been told that by your doctor? I go in next week again to get re checked.