Cervical length.

I went in last week to have my last ultrasound to make sure the placenta had moved away from my cervix. The lady starts doing her thing and she is pushing right above my pubic bone. It hurt so god damn bad. She kept saying your baby’s head is so low I can’t tell if the placenta is there or not. She said okay I’ll come back to it and try again. So she is doing her thing checking everything fluid, cord, all that. Then she goes back and can’t get baby’s head to move out of my hips. To be expected I am 33 weeks. So she does the transvaginal ultrasound, she measured my cervix which is 2.4 in length. Question is is that a good or bad length? I have had 2 prior deliveries delivering at 34 and 36 weeks. I had my cervix checked weekly with my second and had her early due to pre eclampsia. I am just curious about this ones length of the cervix??