When I got mojo about 2 months ago he was not leash trained at all by his previous owners but he knew how to walk nicely on a leash and he didn't drag you around everywhere. Over the past week I've noticed he's starting pulling on the leash. I'm not really sure why but it's getting worse each day. So I've started basically from the beginning and starting loose leash training. Just after 10 minutes he caught on to what I wanted him to do. He's not pulling as much anymore. Of course I don't want him to pull at all so we'll be working on this until it's fixed.

I haven't been doing anything different than I did when I first got him so I'm confused why all of a sudden he started jerking me around on the leash. I know that he wasn't taught but he knew how to walk nicely on a leash even without being trained.

Any ideas as to what may have happened?

It may simply have to do with him gaining confidence. Its not uncommon for dogs behavior to change once they become comfortable in their new surroundings.

He might also just be interested in new things. It is normal for a dog to test you every once in a while. Just keep up your training and don't give them an inch, because they'll take a mile.

He probably just got more confident about his surroundings. Just keep being consistent.

Distractions are everywhere for a dog. Smells, movements, you name it. I let Rex have free time on leash, then when I call him to me, with a "Let's walk" he had better be by my side and loose leash. If he pulls, I turn and go in the opposite direction, and he hurrys to get back at me.
Its funny, sometimes he will try pulling when we are informally walking, but if I say "heel" he is perfect. He then knows that we are working I guess. You are doing what you should be doing, and that is letting the dog know what it is you want.