domain name/url trouble

I host/maintain the following blog/website:

https://rinehartclinic.org/

As you can see, when you access its home page, it has a simple URL that fits the name of the site owner, the Rinehart Clinic.

… However, if you click on any other page or post, you get my personal blog/website domain attached – https://www.tillamookcountypioneer.net. For example:

https://rinehartclinic.tillamookcountypioneer.net/?page_id=16

https://rinehartclinic.tillamookcountypioneer.net/?p=160

… Etc.

Any idea how to fix this? Thanks!