Crush turned girlfriend

I wasn't completely positive on which category to post this under, but this story does contain homosexuality, so if you're not okay with that, please leave instead of leaving harsh comments. I've been berated for my sexuality before. With that done, onto the real topic. I recently started dating the girl I have been crushing on for over three years. Great, right? Not as much as I thought it would be. She's really amazing and I was elated when she said yes. We've been close friends since the start of junior high and we have been barraged with question after question if we were dating and I have been longing to say that we were for so long and now I can! We were basically to the point of unofficially dating without kissing before I asked her out, but now that I have, I've been having this really unsettling feeling in my gut, like this relationship isn't going to work out, or that it isn't meant to be. I don't want to break it off so soon, but I can't shake this feeling that I'm somehow preventing her from marrying some guy and having children. I feel like I'm ruining her life and future. It's her first relationship and I don't want to keep her from fully developing her sexuality before fully committing to being a lesbian. I really like her, but I'm not sure if I should hold off on really dating her to give her a chance to explore or if I should see if things get better. Sorry for the long winded speech, but I'd appreciate any advice I could get. I'm really conflicted here.