ultrasound worried ! PLEASE HELP

Letty
As I read more about your first ultrasounds the more I worry about mine. I went in and they told me I was 6 weeks, I couldn't see anything but a "sac". They didn't tell me anything about listening to a heartbeat or seeing the heartbeat. As I downloaded this app and started learning more about babies, I learned that most listen and see the heartbeat at 6 weeks. My next app is until June 22 at 12 weeks and I am now worried that i never heard my babies heartbeat. Am I being a bit OCD? I've had a miscarriage before and I would just hate to go this month thinking I have a baby on the way not knowing if it's healthy. Should I wait on it until my ultrasound?am I being over dramatic? I'm kind of embarrassed to go back and make them listen to my baby's heartbeat but this wait is killing me :(  and the more I see 6 week ultrasounds mine looked nothing like that! 
Here's a picture of the only thing I saw. It was really that far away and I didn't see anything move nor a baby inside. I actually didn't know what to expect I wasn't prepared for what to look for :(