So I wake up the other day and realized that my last tooth in the bottom left side of my mouth started hurting. And so I took a look at it in the mirror and there seemed to be nothing wrong with it. And then I felt it and when I smelled the saliva it had I very bad odor. What could this be?

I could be incorrect, but to me, it sounds like it's decayed and that you just can't see where it's decayed. I know that when I have had a tooth that is badly decayed, that there will be a bad taste as well as smell from my mouth.

We do have a dentistry expert on this site whom I'm sure will be along to address your question.

Clough is right, the tooth could have a cavity between it and the one in front or at the very back of it where you can't see. It is possible that the wisdom tooth (if the tooth you are talking about is NOT the wisdom tooth) may be infected. The other possibility is that you have a gum infection in that area. I suggest you see your dentist and have him take a look. In the mean time, brush the area well and rinse with warm salt water.