Re: Head butts to the cervix.
A couple of mine have, and Hiccup likes to every few days - lovely, isn't it?!
FWIW, I've never had any cervical changes from it until labor started, so I wouldn't worry too much about that unless you have a history of incompetent cervix or preterm labor.
If baby is head down, it often is them turning their head back and forth, which grinds/rubs on the cervix. It's a strange, not-so-pleasant feeling!