Just Want to Quit!

I have wanted to be a mom my whole life. Since I was 9 years old (young I know) what can I say, I love children! My job, and future career all center around children I'm passionate about it. I've been a nanny, childcare provider, and hope to be an owner of a child care center myself one day... I'm 27 and married I've waited this long and I can't get pregnant. I'm so depressed. I see people getting pregnant so easy that don't even want children and it breaks my heart. I got a positive pregnancy test one day 3 days after its negative. It's like I am being mocked. I'm so upset that now I feel like I'm becoming an obsessed freak. I just wish things would move faster I'm not getting any younger. I'm to the point of just saying forget it. It's not gonna happen at this point.