I'm twenty years old and never have been kissed. Not because there haven't been opportunities but because when these opportunities arose they were always with boys and I just wasn't interested. Because of this, I have thought of myself as asexual for the last four years. This summer I got to talking about asexuality with this girl and I revealed how uncomfortable being romantic/ sexual with men made me and she ask "what about women?". Until then, I had never really thought about it. Now, after three months of thinking about it, I am almost positive I am gay. I really want to get out there and experiment a bit, but I go to a large school with a large LGBTQ+ community ( which is great, don't get me wrong) but I never feel queer enough to take part. It seems like everyone I know in that community has known they were _____ since they were born. I don't really relate to that narrative. I don't feel comfortable going to LGBTQ+ meetings or going on dating apps for fear that people will think I am not queer enough. "how can she know she is a lesbian if she has never even kissed a girl?" type of thing. Writting this out makes it seem silly, but if anyone has ever had similar fears/ concerns and can share how they dealt with it, that would be great!
I largely have felt like you do, so it's not uncommon. My feelings are trickier still and go up and down randomly, but you seem to be pretty sure about how you feel in the main. You shouldn't think that you have to be manly or mannish because you're a lesbian/bi/etc. That's a stupid stereotype that needs to die anyway! You're wonderful, you matter and we are all behind you.
I hadn't known that I was not straight, let alone trans, until I was a teenager. I do get conscious about that at times, and I have felt like I needed to lie to others about how long I'd known. However this is fairly uncommon and I usually tend to be honest to others about my experiences, in order for others to realise that not every LGBTQ+ person follows the "knowing since they were born" narrative. I can't speak for everyone, but I personally wouldn't question someone's "queerness" just because they don't fit into certain stereotypes. Nobody should, as there is more to being LGBTQ+ than fitting into a certain mould. Besides, there are many people besides you who either are not stereotypical or did not know all their lives. As for those LGBTQ+ meetings, perhaps it would be rather beneficial for you to attend as you could use your experiences to enlighten people on how much variation there is among queer people. If the people a the meetings are good and understanding, they shouldn't deny your sexuality solely because your experiences aren't exactly like theirs.
Twenty and never been kissed. Well yeah it will be hard for you to know the truth if you don't kiss a girl you really like. To be lesbian you have to want/ desire to actually sleep with them and want to grow old with them.
The old "how can you know if you have never etc.." is the sort of thing that people at LGBTQ meetings don't say. Because they've probably heard it before themselves. And they know the response: "How did you know you were straight before you etc...?" If you don't fit the stereotype, that's OK: you fit you. Anyway, good luck. I can confirm that kissing a girl is awesome.