If you have a parent that you're close to, you might want to go to them and ask what is going on. Do it in a non-confrontational way. Remember, you're a child in this family. It's not your job to keep your parents together - it's their problem to work out. Try not to take sides in this. I've been where you are and it's generally not pretty.
I had other siblings that I helped raise, so that kept me busy. I was involved with choir at school and babysat for neighborhood families in my spare time.
If there is a friend that you can talk to about how you're feeling, do so. Keeping everything bottled up is really not good. If you're having trouble with your school work, talk to the counselor there to see if you can get some help. The marriage may be failing, but you don't need to go down with the ship. Good luck.
Talk to them .. As much as you are entitled to input in your family's issues, your parents have to work out their problems one way or the other. Hopefully, they can come to an amicable way to deal with their problems .. Even if it means divorce. Believe it or not, some people become better freinds AFTER they divorce. Divorce is not always 'the end of the world'. There are somethings far worse.
First of all, if they do divorce, Understand that you didn't cause the break-up, realize that you can't fix it, and always remember that it's not your fault.
And you will survive if it happens.
I know living with this kind of uncertainty can be extremely stressful.
Talk to the parent you feel most comfortable with as Danae Hitch suggested. Tell them you are very upset because you have come to think that they are thinking about a divorce and let them know how upset that is making you.
And also as she suggested, find a friend or counselor that you can talk to.
I am sorry your family is going through this. I know it is hard on everyone involved. My parents split up when I was 13.
You need to talk to one or both of them and let them know how stressed you are. If you don't feel like talking to them, maybe talk to an aunt or uncle, or a grandparent.
Unfortunately your parents might be so entrenched in their own emotions they are not realizing how much you are hurting. It doesn't mean they don't love you. It just means they are human and overwhelmed.
I am sorry darling, here's what you need to do :
1. Tell your parents no matter what happen, you still love them
2. Ask your friends to cheer you up
3. Distract yourself by learning new music instruments or join volunteer project