Can't get more than to pages of older entries

I’m having trouble with showing more than 2 pages of “older entries”

I have a blog with 13 posts so far, and when I set it to show 5 posts on the first page I expect the rest to show up on the following pages, 2, 3 and so on. But this dosen’t happen. Whatever I do, there’s only ever 2 pages of posts and page number 2 always only show the tre last posts.

So if I have 5 post on the first page, then there’s 3 on page number 2, but it’s the 3 oldest, and the ones in between (number 6 to 10) is gone. But they show up if I increase the number of posts on the first page and in my categories.

It’s not something to do with the plugin (pageNavi), since it’s working on my other blog, and I have tried other plugins and code-bits, but still the same problem. I have a theme called OpenAir by Woothemes.

Does anyone knows what this is and how to fix it?

The site i located at: https://www.blogg.qvarnstrom.nu