3-3.5 cm at 18 weeks — is this really short?

Hi all! I am currently 18+4 with our double rainbow (so definitely more nervous than normal).

We had a scan on Friday and they checked my cervical length. It wasn’t by my usual doctor, but she did say that for my gestational age the cervix is kinda short at 3-3.5 cm. I have a low lying placenta too but it’s not in the cervix.

Everything I read online plus via AI told me that this wasn’t bad at all but the doctor made me worried. How bad is it really?

I got no idea if there is any funnelling, it was a tight-lipped German doctor and one thing I hate is that I need to beg for any information here. I started taking progesterone again by myself, she didn’t want to give me anything.