Should I go for it anyway?

I've fallen in love with my dad's best friend. I'm eighteen, and he's 35 (same age as my dad). We definitely flirt and I'm sure he's at least into me physically, but my dad claims he'd never let me and Andy (my dad's best friend) date. We're together almost every weekend, we have a lot in common, and I think about him every single day... I even dream about him at night (I know, cliche). I'm usually good at relationships and advice, but it's hard for me to be objective when he's clouding all of my thoughts on the situation! Some advice on what to do would be greatly appreciated... and would I be a horrible daughter if I went for him anyway?