...Anybody a dentist? :(

I got a cavity filled Thursday. On the xray it looked normal, but when they went to fill it, it went almost to the other side of my tooth. The xray didn't show it because it was at the cheek side, going towards the back of my mouth, rather than upwards towards the roots.
So when they drilled the nerve got inflamed and the filling is messing with the nerve.
Now it is Monday, and they told me to expect some sensitivity, but this is not sensitivity. This is extreme nerve pain--it radiates through my teeth, down to the bone, into my jaw, my TMJ, even to my ear.
It hurts so bad. I want to knock the damn tooth out.
So I went back to the dentist, they want to do a root canal. They tried a lot with the filling and even put in two special pastes to try to heal some of the damage.
It hurts something awful, and I'm scheduled for next Tuesday to get another root canal. This is my 3rd one in the last year because the decay is so deep in my teeth.
I'm 17 years old. At the rate this dentist is going I'm going to be "dentally challenged" by the time I'm 25. I'll probably have dentures.
As it is the crowns on my root canaled teeth aren't permanent (insurance won't cover them) so I have to get them pulled off and replaced within 5-10 years anyway.
The fillings are like none I've gotten before--not white composite, not silver metal. They are gray and pasty looking. What the heck is that? :/
Should I seek a second opinion? I want to go back to my old dentist but she is in pediatrics. She doesn't work on adult teeth. :/ I don't know if she'll see me, and if she does, I don't know that she can help.
Does anyone know what these fillings might be made of, and if they are contributing to the nerve pain I'm experiencing?
It's keeping me from sleeping, and it hurts without me biting or drinking something cold/hot.
Mostly I guess I felt like explaining my situation. It sucks. I should have brushed and flossed my teeth more--and more efficiently when I did it.
Bad teeth run in my family already.
Advice?
(The dentist said my frenulum is weird. Funny he mentioned it because when I was younger the orthodontist and dentist wanted me to undergo an upper labial frenectomy. Hmm.)
Shellie

I'm not a dentist. In fact, I haven't been to a dentist in about 27 years. My teeth are fine. If you would like, I'm sure I can pull your teeth for you. I won't even charge you for it. And, if it makes you feel any better, guys like women with no teeth.

I've had 3 root canals as well, and as a matter of fact, I just had one done exactly a week ago.

My dentist and I have decided that in my situation, an Endodontist was the best person to evaluate me, considering my chronic dental issues. My last 2 root canals were performed by Endodontist, and I recovered extremely well.

I have the temp filling you are speaking of, and i'm not sure about how it may or may not affect the nerve or tooth itself...

The longer you put this off, the more it's going to hurt, the more expensive it's going to be and the more you're going to regret it.

Also, if you have a root canal done, you need to make sure the person who's doing it is doing it properly. That's why I think you should consult with and Endodontist (specialist) You can have your dentist recommend one...because let me tell you...if you have it done, and it's done WRONG...this pain you're feeling now is like a hangnail to what THAT is like.