Amy Rose - at 12+4 I had exactly the same. A sudden gush of bloody water, followed by a large amount of blood loss after. It was horrible & we were told to expect the worst. However a scan the following day showed baby was fine & that the bleeding was outside the placenta (I'd been overdoing it & was told to rest). Im now due to meet my baby boy in 10 days.
Please don't give up hope. I know it's easy for me to say, but if the bleeding has subsided it may not be as bad as you think. I truly hope everything is ok for you & will be praying for you. Put your feet up in the meantime & lots of love to you all xxx