I came out to my dad, he thinks im attention seeking?

I agree with the others. You've done your bit, just cause he's in denial or doesn't wanna believe it doesn't mean you have to do anything.

He'll know it's not attention seeking if you just leave it and casually mention it every now and then. The worst thing to do is try to prove it, because that will look like attention seeking.

It doesn't matter anyway, dads quite often like the fact that they have lesbian daughters. Means no boyfriends to beat up for impregnating their daughters :')

Okay, that last bit might be a bit of an overexaggeration... but yeah... just leave it for now. You've told him, end of :)

I would just say something along the lines of "Fine, believe what you want. It doesn't change anything though. But then, I guess my sexual preferences aren't any of your business anyways." In a casual, non-bad attitude tone of course.

Because it really isn't his business anyways. He'll learn when you bring home a girlfriend and show that you're serious about her.

You've told him and if he refuses to believe it, then you don't need to explain anything anymore. Only when you start dating, he might remember something you had told him before.

Could just move on with your life regardless of what someone says

Hes trying to convince himself because he doesnt wanna believe it