First Ultrasound. Super nervous

I just made my appointment for my first prenatal visit. I just got a positive test Saturday. My last period was the second week of June so the receptionist told me I would be about 8 weeks right now, BUT I have irregular periods so she said they will do an Ultrasound to date how far along I am. I was testing throughout the month of July and received negatives so I'm guessing I ovulated later and I'm only around 4 weeks. Can they still see this on the Ultrasound? This might be a dumb question, I'm just super nervous since this is my first pregnancy.