How do you explain it to them?

How do you explain to your friends, who all have kids, that it just hurts you to see them with something you can't have?

How do you continue to plaster a smile all over your face when yet another one tells you they are pregnant with the biggest smile on their face?

How do I do it??? Not very well. I smile and ooh and awe and hold babies... And go home and cry in the silence of my room.