advice please

Hello, so this is my 4th pregnancy and I have 2 beautiful girls and I had a miscarriage. I am currently 5 weeks 2 days and last night I was having very bad cramps and pain in my right side. So I went to the ER and they said my hormones we right on track but when they did the ultrasound all they could see is the sac nothing in it. They said it could just be to early to see anything and to follow up with my OB in 48 hours. I'm starting to stress because my miscarriage before there was never anything in the sac I'm so afraid I going to lose this baby too. I still have morning sickness and super tender breasts no bleeding. Anyone else experience this before?