I'm no sodding martyr !
Yes, my ex- was a trollop but there were many (mainly straight) who were quite happy to accept her 'it's because I'm bi-sexual' line.
If she had had a series of linear relationships, boy-girl-girl-girl-boy, etc. that would have been one thing, but to s**g men whilst she was with women, or vice versa because she was bi-sexual and ' couldn't help who she fancied'......!?! does the bi-sexual cause no good, at all.
Yes, of course, it is possible to fall in love with a person of either gender regardless of your own........but if you are proposing to be in a monogamous relationship, then that relationship will be, by definition, gay or straight. If on leaving that relationship you are receptive to establishing a new relationship with the person who attracts you most (of either gender) then you are bi-sexual. If you go out at nights to pick-up/get picked-up and you don't mind what the trouser contents of your amour/euse then you are probably sexually ambivalent and will settle down with age to be either gay or straight.
I know very few bi-sexuals, now. They eventually found someone with whom to be exclusively gay or exclusively straight. Even the footloose and fancy-free have eventually settled for grazing on one side of the fence.
I'm sorry that my actual, factual experience (and I'm by no means alone on this) and subsequent well-informed opinion doesn't tally with your wishful views.........
.....but hey-ho !