Help! Please?!

Alicia
I'm going crazy. After my ultrasound today I was told baby is measuring 2 weeks behind. I am so afraid we are losing this baby. I should be 7 weeks based on my LMP and everything I know about ovulation and conception. My LMP was May 1st. I ovulated sometime between May 14-17th, and got my positive test on May 30th. 
Baby is now measuring 5 weeks, no fetal pole, no sign of a heartbeat. I'm a wreck. 
Could I have ovulated LATE, conceived around the 24th, and still have gotten a positive HPT as early as the 30th? 
What do you think? 
Could my dates just be off, and baby be ok?