FTM - I don’t know anything lol

So at 25 weeks my cervical length or thickness (whatever it is) Was at 3.0 cm but at my 31+3 it was 3.8 cm. I thought it was supposed to start thinning out, not getting thicker ? Is this normal? I see my doctor tomorrow and I’m going to ask anyways but is this a cause for concern.

I’m 34 weeks on Friday and I had a growth scan on Monday. I’ll get the results of that tmr.