Part of the problem is parents don't understand "signals" and things you may think is obvious to them. They most likely just don't understand why you don't do this or that.

Next have they ever really did anything except yell ?

I agree Fr-Chuck, in order to advise correct advice we need to know what we're dealing with here?

You state that you're scared of your parents? Whatexactly scares you? Yelling, punishment, physically scared?