sorry to hear about the loss of your twins. I havnt experienced a loss but can recommend some great boards on ivillage. I have many friends on the parenting boards who have suffered loss and have gone on to have babies.
there are a few that may help you:
trying to conceive after loss http://messageboards.ivillage.co.uk/iv-ukpbttc al
My friend lost twins many years ago, they were born prematurely and died at two days old. It took her seven years to get pregnant again (I'm not suggesting it will be the same for you!) but when she did she had a cervical stitch. That pregnancy went fine and she had a little girl, just a few months later she was pregnant again, again had a stitch and had a little boy, who although he was six weeks early was fine.
my mum miscarried twins and i think it has stayed with her since. however it never made her give up and she has had children since. and if it weren't for her being in her mid fifties she would have many morexxx hope you are coping ok and im so, so sorry for your lossxxx