How do you know for sure if you are straight or not?

I've never been with a woman, but lesbian porn turns me on. I've always had a boyfriend & find men very attractive & feel as tho I'm "happy", but I really am just not that into the physical part of it as much I I feel like maybe I should be I don't really know if it's a normal amount or not. Is this just bc I haven't found the right guy yet or could I maybe be bi or even a lesbian & just dont know it? I'm very confused & appreciate any advice or similar experiences. I just wanna be happy. I feel like I care about my boyfriend & don't wanna be with someone else but I still feel like something's missing still maybe or like I'm just going through the motions & not as "fairy tale" perfect happy as everyone else is. Am I just a cold person w/lack of emotions & feelings?