First ultra sound

Today I went in for my first ultra sound for the pregnancy.. I was scared to death becausey my last pregnancy ended in a miscarriage.. W/ my last pregnancy my first ultra sound they didn't see anything.. Well today They only found a tiny tiny tiny sac in my uterus & they said it should be bigger since I'm 7 weeks, then they said it could be an early pregnancy & their dates could be off but I'm nervous I'm getting my blood drown every 2 says then if my blood work doubles I'm following up w/ another ultra sound.. What do you guys think??? It am early preganat or another miscarry?