Baby sister had a baby, and MY HEAD POPPED OFF

i am 25. My sister is 3 years younger. She got pregnant, unplanned, with a guy she hadn't been dating a year yet. I'm happy for her, but I'm so sad, mad, depressed, frustrated, disappointed ect.. my fiance and I have been together for 7 years. never used protection and never even had a maybe. I want to be over-joyed for her, but I see the way my parents treat their daughter and now grand daughter, and it kills me becuz I feel like I should have been the one starting a family. my niece is now 5 months old, and I have yet to meet her. I tell myself it's becuz they live 8 hours away, but I KNOW it's becuz it will just hurt too much to see someone get on accident, what I've been working so hard to get.