7 weeks 3 days ultrasound help

I'm 7 weeks 3 days with baby #2, according to my LMP (Jan 14).

I went for my first ultrasound today and I am only measuring about 4/5 weeks. Should i be concerned? I'm waiting on a call from another doctor so i can get a second opinion and hopefully a second ultrasound today. But I'm curious if anyone has been in a similar situation and what the outcome was. I found out I was pregnant on Feb 8th so it just doesnt make since to me.

Thanks in advance.