Is it true that you said you are happy and proud of your good grade in English? That's a good thing I will say. Whatever the thing is, no matter how "small" it might seem to you/other, I say rely on that "small" happiness. I think your dad is being illogical though, studying for 12 hours? I doubt anyone can do that. Even people without illness will go "crazy" by doing so. How about do a little strategy? Study when your dad is about to leave house and then study again when he's about to come home. That way, he will see that you are always studying?

I know lying to our parents is a bad thing. But if doing what they asked us making our condition even worse, I believe they don't want that to happen either. Besides, if we are getting more and more stressed out, we won't be able to study anyway right? Better to study just a few hours but fully concentrate.