I know you said you feel you cannot say No to going to your parents' house.

But fundamentally speaking, you're betraying yourself by going. It is obviously a bad situation, and there's no benefit to you at all; there's only bad stuff.

What about afterwards? Chances are, there will be lasting effects that only you know about and have to face on your own.

So, yes, saying you're not going is going to be hard, absolutely. But is it as hard as the situation you'll be in if you do go? If you don't go, you'll be reclaiming a bit of yourself and your dignity, not for them, but for you.