two gestational sacs, one heartbeat

Sarah • TTC since April 2016. MMC #1 Sept `16 MMC #2 Jan `17 Ectopic and Tube Removed Nov ‘17
Anyone experienced this?
One sac has little baby in strong heartbeat but a bit smaller than worked out, the other sac measuring about 3 times bigger than the baby one and is evidently empty. 
I'm scared it's going to push baby out :( and I've got a bicornuate uterus as well, and both these sacs are in one side so a bit overcrowded! 
Can anyone please give me any information? I'm scared this is going to end in another miscarriage :(