Through "Number of posts on main page" setting in your blog, you can configure how many posts should be displayed per page. But sometimes Blogger only showing very few posts per page, not considering that setting.
Blogger has introduced a mechanism called "auto pagination" to reduce the loading time of its blogs. This mechanism is to show less Blogger entries per page if it detects that the page is heavy to load.
To avoid this auto pagination happens, you can try to decrease the loading time of your Blogger blog, some recommendations are:
1. Use Blogger "After the Jump" feature (read more) in your longer posts.
2. Reduce image sizes/ optimize images.
You can use a software like Photoshop, GIMP or free online image optimization service.
3. Remove unnecessary widgets.
Do not use many widgets on your blog. It will cause to more problems.