I think I despise my dad
Did you tell your dad you despise him?
I didn't, and I don't think that the feeling will go away
It's normal for children to feel respect for their parents, and you should be loyal to your family, just as they are to you.  It sounds like the problem is something that can be solved if you just talk to him about it.
I can't talk to him about this.
Is there a reason you feel this way? I know its hard, but your problems will not go away unless you talk to him. Just start off slow.