Question ladies

Hey my name is Stephanie I'm 27 and just found out I'm pregnant with my second child I currently have an almost 3 year old ...my last period was on  July 28th and I ovulated on the 12th of this month so that would make me 4weeks pregnant I had an ultrasound today which I don't know why they did one cause there was no sac or anything I'm guessing because I'm so early my hgc i think that's what it's called was 25 is this normal ? I've read yes because I'm so early but just wanted to confirm !