So I had an ultrasound..

I have twins I an 5w and 3days one had a heart beat and the other one didn't they want me to come back in ten day to see if the other one is gonna have a heart beat the other one was a few days behind in growth but they said that it could be normal bc I'm so early they are both in different sacks ... I have no idea about twins can anyone help I am stressing out if the other one dose not make it I'm a reck