6 weeks, not 7 weeks after 1st u/s

Heighty24

Hello, I guess I am just trying to ease my mind and see if this has happened to anyone else.  I had my 1st appointment and u/s yesterday.  We saw the baby and the heartbeat!  My doctor said I am measuring at 6w not 7w, but that could be due to late ovulation (I have had erratic cycles anywhere from 27 to 32 days).  She wants me to come back in 2 weeks to remeasure to confirm how far along I really am.  Should I be worried?  Is this "normal"?  There was nothing negative said... but I am just a worry-wart!  Feel like I can't be all happy and telling everyone yet until 2 weeks from now.