Proud Dads

Was browsing Facebook and noticed an old boyfriend has just had a baby. Clicked a friend request through to his old best mate - who was also a mate of mine years ago - and he has just had twins. Am happy for them both, obviously. They will be lovely dads and look very proud and doting. But it is always a sort of blow when you hear this sort of news in quick succession. I have not yet been able to put my finger on why it hurts so very much.
People, including H, seem to see it as petty jealousy. Petulance because someone has got something you have not. But it is nothing like that. Nothing like feeling covetous when someone has a flash car or house or even relationship when you have not.
One of the things I have found the hardest during this whole process is people's lack of understanding about why it can sometimes (although not always) hurt so much to see other people pregnant or with babies, or hear the news that yet another friend is pregnant. I have been made to feel like some sort of ogre on several occasions because of these feelings, which I cannot help and have not always been able to hide.
It is understandable I suppose. In fact, I think even I struggled to understand similar reactions from other people before I was in this position.
Even now, I struggle to explain what it is I feel let alone explain why I feel it. But I know it is not an unkind feeling and does not mean I am not happy for other people. And I know it is not just me who feels this. It seems pretty widespread and maybe just goes with the territory of dealing with the loss, the overwhelming grief of infertility.