Very angry

I feel like i cant wait no longer cause me nd my fiance been tryn ova a year now nd i feel very sad nd what make it so bad.. i already got a niece nd got a another one on its way.. its a shame my own little sister got one nd having a another one on August 19 this year... sometimes i catch myself gettin piss the fck off at times.. this is my first time tryn this ttc app... my fiance already have 3 kids nd i dnt have none.. am i wrong to feel very selfish to myself.. need some advice yall.. very angry right now!!!😤😤🤬🤬