I'm really confused.?

Okay, so I'm turning 20 at the end of this month so I should be old enough to know the answers to this I know. See the thing is, I've slept with guys and I've dated a lot of them but I've never really been 'into' them. It's always felt like there's been something missing and the relationship has ended. I realized I was attracted to girls a long time ago, about 2 years ago to be exact, but I've always ignored it or said I was bi because I feel scared at the thought of actually saying that I'm gay. The thought of never having kids or getting married. I mean I've never had sex with a woman I doubt I'd even know what to do and this absolutely terrifies me but I've noticed that I hardly experience any attraction to guys and if I do its a temporary thing like I want them to fancy me for their approval or something daft whereas with girls I genuinely feel like there's something there. I've made out with a girl and it just felt right. But I don't know what to do. Am I gay or Bi or not? Help.