Help ladies to clear my mind

OK ladies by my period I am 6w4d well I was having some bad cramping so I called the doctor office they told me come in. So I go and they said I am measured a week behind which makes me 5w4d but I did see a yolk sac which he said is normal at this time. He also wanted to check my hcg levels so I have to go back in two days. He said it looks like a great pregnancy but I am nervous has anyone had this done and come out fine I go back in two weeks to get another ultrasound.