Sit down and have a talk with them about how you feel. Explain that their fighting is scaring you and bothering you. You are their child, after all. they can't just ignore your feelings and continue this war. Sometimes parents have to put aside their difference and put their children first. Make them promise you that they will at least try to get along. If they can work past their disagreements, they will see that they don't need to get a divorce. and if they find that they need a divorce in the end, they can't say they didn't try.
You have to talk to them, not only for their marriage, but for your own emotional health. if you can't tell them your feelings now, you never will. and you will resent their choices for the rest of your life.
so please, talk to them about how you feel. i know this is a hard thing to go through, but i have faith in you. you can do it!
Hang in there!