How is it fair people who don't deserve babies have babies?!

So this is definitely a rant. Every month for almost a year now I have had negative test after negative test. It's already hard as it is, but then going on Facebook and seeing my younger sisters friends who are still in high school and even middle school are having babies like it is nothing! It makes me not only extremely jealous, but extremely mad what teenagers are doing to pregnancy. I am 21 years old and I am TRYING to start a family. I know the day I turn up pregnant though, people around my age are just going to think, "oh her too?" People are ruining the beauty in pregnancy and creating a family, and it's torture. I want everyone to say they're happy for me and mean it, but because of the teenage baby boom, I don't think it's going to happen. Why can teenage girls get pregnant so easily after only having unprotected sex for a month or two and I can't get pregnant after AN ENTIRE YEAR?! What are your ladies input and opinions on this?!