Layout screws up only with posts

my URL is

My problem is only on the homepage or with posts.
If you click a category, the header doesn’t show up correctly, which I know what the problem is and can fix.

But if you see , the layout is exactly how it should be. The only difference is it’s a page, right?

I don’t know what’s going on, and it’s frustrating!

(The brown list nav thing is just an image uploaded from my computer in the post, so that’s “supposed” to be there)