I never really questioned my sexuality, but I did have an experience that somewhat confirmed it for me.
I've had a fairly open relationship with my wife and we've brought people in for various reasons, and I had the opportunity to have a devil's threesome with my (at the time) brother from another mother, and during a lul when my wife had to use the bathroom, we kept the mood going ourselves. Found out that I'm definitely not (physically) into AMABs, and they (eventually) found out they were trans. I still love the hell out of her even if I don't talk to her nearly as much as I'd like (damn life always life-ing), and I have a couple non-sexual semi-ronantic relationships with AMABs in my life, and one of my partners is a (semi-transitioned) trans-man.
All that to say, you never know if you don't try. And if you feel that the person is safe/trustworthy/receptive enough, it can't hurt to test the waters and see. You may find out that you're bi, demi or pan. And you might just have your cis-het confirmed as well. But you'll never know unless you're willing to make that step.