Fundal height

A stupid question but does fundal height stay the same no matter what pregnancy you’re on? I know the uterus shrinks down to normal size after so long after baby.

I’m pregnant with #3 & I swear I can feel baby move a bit higher than my fundal height should be. Idk if it’s just phantom movements or what. I’m 20 weeks so the fundus should be level with my belly button, but I sometimes feel kicks about an inch or two above my belly button.