i think with all the different datings is the measurements they get so try not too be too worried n there is a heartbeat sooo yayyyyy!!!
as for the other sak im not sure i know with my ds1 he was a twin n i had an us at 12 weeks n by 32 weeks i didnt know there was another one in there till i was told he had passed..
some can hide and some can be overshadowed so maybe there could be a viable one but just not clear n too early too see... fingers x'd
but good luck hun n the way this yr has flown 2 weeks will be over b4 u know it
keep us updated pls...