Is it normal that i'm straight but..?

I am a straight female, so before you ask I have been with guys and I definitely am straight... I never have trouble with guys turning me on in person but when I'm alone I need to watch lesbian porn to get turned on. But in person girls don't do that to me. You may have seen this question before but here is a twist: I have been anorexic and and struggled with anxiety off and on my whole life, and I think lean/fit people are most attractive usually (not trying to be mean I just usually notice that I tend to go for guys/admire the look of girls that are kinda lean or lanky as opposed to muscley or stocky). But whenever I watch lesbian porn it's always things involving weight gain that turns me on. I'm really confused by this especially considering I'm from a highly conservative family that would probably kill me if they found out I so much as even French kissed someone, let alone watch porn, and may even be bi according to some people I've talked to... Because of this I kind of hate myself for all that's been going on and I just need to know... is this normal??