julie/ong: I think I can help with your question about miscarriages. Most women experience some sort of warning sign - eg cramps or bleeding - before a MC, but this is not always the case. I had a blighted ovum, meaning that the ovum did not form properly after fertilisation/implantation and the fetus did not develop. I had no symptoms - had my normal preggy symptoms, zero spotting/bleeding and just light cramps which went away after a while.
Some ladies have missed miscarriages, meaning that all seems well, then one day they go for a scan and learn that their bb's heartbeat has stopped - again, no symptoms.
For women like us (the symptom-less!), some doctors will suggest a D+C procedure to remove the pregnancy-related contents of the uterus (called "products of conception" - eg: water sac, placenta, fetus, etc) or you can opt to wait to bleed naturally or have a medically-managed bleed (which means you take certain meds to kick-start the bleeding process).
Hope this info helps! Please don't stress. I am sure your babies are fine. Once you hear the heartbeat, the odds of MC are actually quite low. Most of us here had MCs at an earlier stage.