Depends on what you are masturbating to. If its to porn, most likely no. But if it is to ur own fantasies, then yes.
Fantasies are not necessary 100% accurate. In my case, I had plenty of fantasies involving a male and a female. But my interest/attention were generally on the guy. The female was only there because the fantasy required one in a supporting role.
While it can be a good indicator, keep in mind it can also just be your minds way of exploring fantasies you wouldn't otherwise experience normally. If the fantasies involve people you know/are attracted too then it might be more likely.
This is actually a very good question. I have wondered about this same thing. When you are masturbating yourself or a partner is helping you and those sexual thoughts come into play, what does it really mean? Given it’s sexual rather than passion I am leaning towards it’s about sexual needs rather than sexual orientation. I can fantasies all I want about having sex with a man, but if I am not drawn to being with a man outside of sex, I would wonder if I am gay or just sexually needy. Given I am drawn to men sexually and non-sexually, I know I am gay, but I am not drawn to women beyond the occasional sexual fantasy, so I don’t see myself as bisexual or straight. Best understanding I have on this.
I would think so I started wondering if I was bisexual when a lot of my fantasies involved a girl and I sharing a guy
Not really - or at least, it doesn't for me. I watch all different porn pairings - man/woman, man/man, woman/woman, and have a range of imagined porn reels in my head with the same kind of content.
It's not just the sex aspect for some people, it's the type of situation. Some people might get off on the situation more, especially people who might be ace and have a fetish but no sexual attraction to a particular sex or gender.
If it is to porn I do not think it means something well you can pay attention to only one gender and other person is just there. Umm, about fantasies for me I fantasizes about girls and guys but in the end....girls. I think it could show something but you can not be sure..