Ultrasound tomorrow 5 weeks 4 days, what to expect

I have my first appointment tomorrow morning. My docs are calculating my due date based on the first day of my last period but I know that I ovulated 2 weeks late based on OPKs. I told the doc this but they still wanted to schedule me based on my last period. So I'll be 5 weeks 4 days tomorrow. What should I expect on the ultrasound? I'm preparing myself to not see a heart beat but has anyone had an ultrasound this early? What did they see? Thanks!