Jealousy

I scroll through Facebook and see a picture of an old friend's daughter. She's JUST learning to sit up. Cold, bitter, jealousy floods me for a moment. I never feel this way when my nearest and dearest have daughters. I was just happy for my bestie and cousin who had daughters, but jealous of an acquaintance who was due at the same time.bmy other best friend is expecting and waiting to find out gender, but I just want her to get what she wants (she really wants another girl) my husband says it would have a kind of symetry. Fore to have 4 boys and each of my best friends to have 2 girls. 

Anyways. I don't understand. Why do I feel jealousy at all? I have 4 beautiful sons and they are enough of a handful that the idea of another child makes me want to run screaming. I just wish that God would either give me reassurance that I will have a daughter some day, or let me know that "never" is true and accurate, not just the voice sobbing in the background of my mind. I feel that a final answer would help to accept this reality, rather than having a spark of hope that someday, somehow, I will have a daughter to call my own.