Questioning my junk

A friend of mine, who is a lesbian, once told me she could only have sex with a man  who would let her fuck him with a strap-on. I think that's fair. She see's penetrative sex as an inherently dominant act. you can't fuck a person in the way that men "fuck" a person without assuming a certain level of control. I agree with her, and feel that she's right to feel the way that she does. So why I am I jealous that it's another dude she isn't attracted to that she wants to fuck? I'm a straight male, as far as I know. but I fantasize about this specific friend pegging me. Maybe it's because she's hot, she has big tits, etc. but honestly, I wish that she had picked me as her straight choice. I don't think I'm gay. I used to think I was Bi because I was curious, but really the closest I get to homosexual attraction is wishing that my lesbian friend had chosen me to fuck in the ass. I still don't know what to think about that, or whether to tell her. Maybe it's just because I have issues with abandonment and the fact that another guy is her go-to makes me uncomfortable. Either way, I think I have to tell her. Not just for my own well-being, but because I feel weird keeping my attraction from her. She's seen my junk, and I've seen her in nipple tassels, but I don't think I've ever told her that I've been crushing on her for what? 6, 7 years now? Why can't everyone just be bi or pan-sexual? Why must everyone who turns me on turn out to be gay? Maybe she wasn't kidding, and she'd really be down to top me? I guess there's only one way to find out.