I'm Scared Of An Incompetent Cervix. I've Had One Previous

I'm scared of an incompetent cervix. I've had one previous termination and one D&C. I'm now 21 weeks and 4 days. At my anatomy scan at 18 weeks 4 days my cervix was normal length no funneling. My doctor does not think I should be worried. But I can't stop worrying about it. Since my cervix was good at 18 weeks should I be in the clear for incompetent cervix?