So nervous!

kait

I’m 6w4d and had my first sono today. The doctor said the baby was measuring small and asked if my periods were irregular. I told him I had been but only in the 3 months leading up to getting pregnant. He then told me ok not as small as I thought looks like 6w2d. I asked if he saw a heart beat and he said he saw a flicker. Has anyone else experienced this and had a healthy pregnancy and baby? I am just so worried. I go back in two weeks.