No heartbeat detected at first ultrasound

Went for first ultrasound last Monday and couldn't find a heartbeat. According to <a href="">due date calculator</a> I'm 10 weeks but fetus is measuring 2 weeks behind. They also said my uterus is tilted forward (not sure if that makes a difference?). Second ultrasound tomorrow to see if anything changes. Fingers crossed they find a heartbeat. This has officially been the longest most anxiety ridden week of my life. Has anyone had this happen or something similar?