Is this normal to feel this way?

Lately in my life it seems like everyone I know is either pregnant or just had a baby. I am 27 and my fiance has a 2 year old and 5 year old (both girls ) . While I love those kids, I can't help but have a yearning for my own. Sometimes I want my own so bad that I think in my mind that I wish my birth control would fail so I can have one. My fiance wants to wait a couple years until the 2 year old starts preschool at least before we start trying. Is it bad that in my head I'm hoping my pill would fail and I would get pregnant? Of course I would never "accidentally "forget to take it and he makes sure I don't but IDK it's getting to the point that I can't even get on facebook without getting a little jealous or upset when I see post after post of people's child or children and I wonder when it will be my turn. Is it normal to feel this way?