That looks like you're subtracting stitches by accident. Check the pattern for how many chains you were supposed to start with and how many stitches you should have in your first row after stitching into the chains. On a basic pattern every subsequent row should have the same number of stitches as the first. If your number of stitches is correct then it is probably just a tension problem. That first row into the chain is often a little looser than the rest of the piece because it's such a freaking pain in the ass to stitch into chains and get good tension at the same time. It's common (at least for me) to have a tiny bit of flaring out at the base of a project because of this.
YouTube should have some good videos. I'd do a search for you, but I'm at work and can't get on YouTube here. :(