why god?!!

I'm 22 years old, so is my boyfriend. I have known him since the 3rd grade and have been a couple since the eighth grade. we have decent jobs, a huge and perfect apartment. we have cars, we can afford our lives, and have been trying to have a baby for 3 years now. my sister on the other hand is 19 no job, no car, still with my parents, barely got a high school diploma and is now pregnant with her first child from an accidental one night stand. I know I should be there for her but I can not help but feel angry with God or the universe or whatever is out there and envious of her. I can give a child love, affection, and a good life so why have I gone through treatments, procedures, medication, all so that I can get yet another negative test. and yet someone who can not give a child so much as a toy can have one so easily?