HI there
I am sooooo sorry this had to happen to you. I had almost verbatim same experience at 19 weeks with my duaghter and can honestly say I relate with the never been this scared before. I was absolutely hysterical then pulled it together with help DH on way to hospital then when they did the US she had monitor turned away so we couldnt see and was searchign all over for about 2-3minutes and there was NO sound, there had alwayas been an immediate sound of a heartbeat so I completely had a huge meltdown shaking crying hyperventilating and she looked over withe wide eyes "ooho whats the matter baby looks great"--she never though to turn sound on I could have killed her she didnt think about fact we couldnt see or hear and her moving wand all aroudn was becuase Lillian was bouncing all around--not because she was searchign for a heartbeat.
Anyway long story short I was with a perinatologist who said that as long as the bleeding is on the outside not aroudn babies it is not a concern and that it woudl probably happen on and off since it seemed I was already more prone to it. Of course I only had a singleton sdo I am sure having two in there will make itmore likely with extra pressure and make it more scary. They did say that the blood is very irritating to the cervix/uterus so when they did my NST I was not contracting but it was showing irritability which showed up as little spikeys instead of hills so they gave me a shot of terbutaline to calm uterus.
Of course take it easy but also try your best not to worry yourself sick. I did (after the bleed at 19 weeks I had regular contractions from 20 wekes on so I was scared I was going to have a micro premie <img src="i/expressions/face-icon-small-sad.gif" border="0"> or worse )and I wish looking back that I had not, it wasnt good for me--or my husband (crabby wife) and I am sure it didnt benefit my DD either. Definately listen to your body and be watchign for signs of somethign more or go back if you bleed again just so they know and can check for irritability.