Hi hopejoy! Big, big congratulations to you!
I can totally relate to you (except fot the anti-D). I lost my DS at 24 weeks in December 2002 (died after two days) and my DD at 26 weeks - who was stillborn, in August 2003 (both were also natural deliveries).
I fell pregnant again in October 2003 and was pescribed low dose asprin, which has apparently been shown to lower the risk of a subsequent child being stillborn as well as lowering the risk of clotting. I was also had to take 5mg of folic acid as well as Pregnacare as it was found from a Thrombaphylia screen that the gene that handles folic acid has mutated and that I have to take 10 times more than normal for my body to process the normal amount of folic acid (confusing eh!).
Also, like you my two lossed were classed as 'no known cause' which is extremely fustrating as if you knew what the problem was, at least you can take steps to ensure that it does not happen again. I privately think that although I can get pregnant easily, I simply can't hold them.
I'm pleased to say that although my third child (my second DD) was born 10 weeks early (she's fine except she just needs to get a tad bigger), I firmly believe that the aspirin played a big part in ensuring that she stayed in longer and that she was born alive. Like you, I was also scanned every two weeks.
I know its easier said than done but please, don't be scared. You will be so heavily monitored, which should help to reassure you (I practically lived up the hospital!) I also have a couple of friends who had problems but were pescribed aspirin and carried to term.
As many people have already said, keep posting as you will get tons of support here. I have personally found this site to be invaluable and it has helped me alot