Ah, I don't think I fit the definition of what you're asking since I never dated any male, but I did manage to convince myself I wasn't a lesbian for quite some time.

Basically, I'm not very in touch with myself, my body, my feelings. Or I used not to be. And I felt very little. So the one time I would feel something, and it'd be about a man, I'd go "oh must be love," even when it was fear I was feeling. I just couldn't identify any of my emotions. First time I started staring at girls' lips or breasts, at 17, I of course noticed the difference, but I was so ashamed and I really didn't want to be a lesbian I just thought "whatever, it's normal, everyone is a little bi, I can still be straight" and I just ignored the fact I wasn't staring at boys at all. After all, my straight friends didn't talk about boys either, so it was easy to think we were the same. Next, it was the first time a guy expressed interest in me, when I was 20, and I froze and immediately changed the subject and then ignored him forever. Knee-jerk reaction. And I thought "what the heck is wrong with me, I don't want to be alone forever do I?" Then my attraction to women just got stronger and I thought it was society hyper-sexualising women that was poisoning me or something lol. I started worrying, a bit, about how I always, always avoided anything relating to my love life. Friends who talk about it included. But no, it did not click. At this point my brain had become an expert in denial lol. I came up with all sorts of theories about why I didn't want to date men, and not once did "i'm a lesbian" cross my mind until I read another lesbian describing her difficulties accepting herself. And then the dam broke and I spent something like two months recovering from that discovery, suddenly becoming hyper-anxious and sad and feeling like my world was crumbling down to ashes. Which it kind of was, to be honest lol. I had constructed this fantasy world where I could be straight, and in one day it all came crashing down suddenly.

I wouldn't be surprised if this is how it goes for most late-bloomers. The society we live in makes it painfully easy to think attraction to men is every minor feeling you have ever had for a man, be it admiration, envy, and more worryingly even fear, stress, and loathing. And attraction to women is normal because "women's sexuality is fluid" or something. For a long time I bought the lie that female homosexuality just doesn't exist. First time seeing (or reading) someone like me was what did it. I'm grateful to all lesbians who share their experiences and hardships, as well as describe their feelings and desires so clearly, who write blogs about it, because I would have realised way later without them. What cemented it and shut up the obsessive "what if you're just fucked up" voices in my head was actually flirting with women and being sexual with them and seeing just how easy that was. Simply something I actually wanted. And I thought "wow, all this time, this was how people actually felt when crushing on someone? I finally get it"

Ironically, I have never felt more like I belonged with my fellow humans than at this moment lol. Desire and love are just so important, and I am so glad I will never again live my life without feeling either, now that I know what they are.