scary first appointment...

So I went into my appointment today thinking I was 7 weeks based on my last period. I started Aug 22nd. Believe I ovulated September 7/8. All they asked when I scheduled my appointment was when my last period started and then they scheduled me for 7 weeks from my first day of last period (the 22). I go have the sonogram all they see is a sack and a yolk sack. So they believe I am only about 5 weeks. So no heartbeat. Then I go back to talk to the doctor and she is confused why I'm only 5 weeks along but my last period would suggest I'm 7 weeks. So they will check my hcg levels Monday and hope they are a 15 or more and then bring me back in Tuesday for more blood work to be sure my levels are in fact rising as they should then bring me in for another sono in a week and a half or so. I of course left the office in tears even though she said the fact there is a sack and a yolk sack and based on the size of my uterus during my pelvic exam she believes everything will be ok but has to be tell me about the possible of the worst bc that's her job. So now I have about 5 days of trying not to worry and believe that everything is in fact moving along as it should be. If this has happened to anyone please reach out to me, I'd appreciate it.