Confused and not sure what to do :/

Okay guys, so lately this guy has been messaging me and he’s absolutely the sweetest guy I’ve ever been in contact with. Ive never had a boyfriend or a girlfriend before btw. I have always known since I was little that I was into girls and so I figured that I was just bisexual. However, this guy that’s been messaging me is making me think that maybe I don’t like guys. I’m just not into him in any way and it’s not like it’s just him, it’s all men. I feel like there’s something wrong with me because he is amazing and he sent me this long goodnight message telling me how great I was and all but when I read it, I just felt so awkward and weird and I thought that if it had come from a girl I would’ve been happier. I feel like I SHOULD want him but I just don’t. It occurred to me that when I think of my future, I’ve always thought about having a wife and thinking of marrying a man is so unappealing but marrying a woman sounds like a fairytale. I know in the past I’ve “liked” guys but I don’t know if that was real or if I felt like I had to because of the heteronormativity and my mom always saying “you’ll find a man.” I find some men attractive but I’m not actually attracted to any of them. This guy wants to date me and I feel so horrible that I’ve been flirting with him because I’m afraid to be mean or tell him I don’t like him like that because he’s too sweet. And I don’t want to tell him I’m a lesbian if I’m not but I can’t stand the thought of leading him on. Calling myself a lesbian just feels right to me though I’ve never even spoken to a girl in that way. I know this might be hard to understand but I just need help. How do I discover who I am and who I’m attracted to? How do I let this guy down gently?