Yeah, that's pretty much exactly what it's doing. That's tumblr's design by default. One can customize it but it takes some time and knowledge. Some people prefer the endless scrolling (me, for example). My blog is mostly default. One thing you can do is look through the archive. It gives you little thumbnails to browse and you can click on what you like to see a full size and can reblog it.
I used to fuss with fancier blog designs but it's not worth the headache imo.