I hesitated to post again, because the OP is really having a hard time now, and she has my sympathy, but I do want to say that I don't believe it has to be this way (although I do think that many people just assume it's natural for teens to be horrible).
We all live different lives and have different circumstances, so I don't mean to come across as having all of the answers, but I don't think it has to be this way.
I can say without any question that I never behaved that way, because my parents would not have tolerated it. Did I think stuff? Sure I did, but I knew better than to say it. To this day, I would never consider being disrespectful to my parents.
I can honestly say that DD (almost 19) has never screamed anything at us. I'm sure she's like me and has thought things many times, but she knows better than to say it out loud (self control is a good trait to learn). Is she a perfect child? No, she's not, but neither was I (nor am I now for that matter, but I don't scream at her, and when I make a mistake, I apologize to her).
We started when she was young, and she was always made to behave (unlike some relatives I know with their children, we didn't consider it "cute" when she acted up). We also never said, "We just can't do anything with her" like I've heard other people say. There was always some punishment that could apply. As adults, we were in charge - not her.
She horse shows and was always taught the proper way to behave there too (you don't mouth off about the judge or other competitors). When she was about 15, she came out of a class angry about the placings and started to "mouth off". I quietly told her to go untack her horse and load him in the trailer. She said, "But my classes aren't over!" I told her that yes, they were (keep in mind that we had money invested in those classes, plus the money getting to the show, time, and there were points involved since she was leading in the classes). On the way home, we had a long talk about how we behave in public and that right or wrong, the judge has the final say so. Furthermore, we're there to have fun, and if she's acting like a brat, we aren't having fun (and it's way too much work to do something that we don't enjoy too). That never happened again. She wasn't always happy with the placings, and we might discuss it in the truck on the way home, but she didn't mouth off publicly.
As someone else said, we always taught the concept of consequences. We also taught that just like there are "bad" consequences, there are also "good" consequences. When you act like you've got good sense, you have a lot more privileges and the respect of people who matter (DD has had a lot of adults go out of their way to help her achieve things solely because of her good attitude and work ethic, and she can really see that).
So, no, I don't think it has to be horrible. Yes, there are hard times sometimes, but your children don't have to grow up to be obnoxious.
Again, JMHO.