They saw the sack at thescan..but im still bleeding

[pinkpanther]

im 5 weeks preg, i had conceived thru IVF!
my RE said bleeding may happen as the body could be flushing out incase of multiple embryos... i.e, its possible it could be the other embryos flushing out.
but im very surprised i was bleeding v heavy last night and thery were able to locate the sack this am... im using 3-4 pads a day..and i wont call the bleeding light .
So has anyone experinced anythin like this?
4 embryos were placed?