Can an untreated cavity become deadly? I'm freaking out.

[KatherineGood]

Okay. I noticed small black hole on the side of my top right, second moler. I noticed this about 6 months ago, it did not hurt, and since I have no health insurance, I put it off until later. I occasionally had some toothaches, nothing bad, mild, tolerable pain. I usually took some Motrin, and it took the pain right away, the pain usually stopped the next day, and never returned for a few more weeks. Now that its November, about 6 months from when I first found out, and now I'm in excruciating pain. My entire jaw is hurting, both top and bottom, its a very sharp and dull pain. I have been using off brand headache relief (which also states it takes care of toothaches) its working pretty darn good. Sometimes if its really really bad, it wont take all the pain away (just makes it more tolerable). I cant stand the pain without taking something. ice pack, and numbing stuff does not work. I know i need to go to the dentist soon, I actually plan on calling sometime this week. Knowing me, I am one to search on the internet for every possible outcome, and I am now in full panic of some sort of abscess or infection spreading to my brain, or  me possibly dieing. I'm FREAKING OUT PEOPLE:( I need some answer's. pronto, I'm driving myself nuts.
(PS. I also have a headache that sometimes comes along with the toothache on the same side. )