As the mother of an 18 y/o who can at times be a REAL butthead, I will suggest sitting down with your parents for an honest chat. Y'all need to find out what the issues are, although I suspect you already know. Are you behaving maturely? Are their expectations too high? What exactly is causing all this stress and screaming?
Once you get to the crux of the issues, hash 'em out. Maybe you need to do more around the house or pay rent like Teresa said. Maybe you need to look into getting an apartment in the town you're already in, until the program finishes. I'm not there so I can't say. But I honestly believe you should at least try to work things out with your parents.
Like Teresa, it wasn't until I had long term guests at my house that I figured out why parents wig out all the time. It is sooo frustrating to be responsible for extra messes, extra food and bills, not being able to run around nekkid if ya want, etc. Especially if the "guest" (or child) seems ungrateful and/or unwilling to help out. The power & water bills go up, the grocery bill goes through the roof, dishes stack up twice as fast... and here's this extra person just sittin' on their butt, lol.
Just my perspective as a parent. I love my son to death, but some days, I just wish he'd freeking move out already.
Of course he's not even out of high school yet.... lol