Leigh
I am so sorry for your losses, and I can relate to where you are coming from but not on as large scale. With each of my losses I had a friend that was due at a very similar time to me and I still struggle with the knowing that I would have had one at that age even now. Something that I don't think you ever get over.

You just smile when your friends have their babies and wish them all the best and then get on here and vent.... It is the only way I made it through.
I am also on the other end of the scale too now, I have a friend who was due tomorrow and I am due on the 20th, two days after. She miscarried so I am incredibly aware of how I felt and will personally call her when this bub arrives and let her know. I have already sat her down and said if you don't want to see me for months after the birth I understand. She says she will come and see me but I don't think you quite know how you will handle the situation until you are in it.
Just do the best you can for your friends and you are allowed to be jealous and hate them from the inside, just come in here and talk to us, we know!
take care and good luck!