should i worry if there was no heart beat at 6 weeks

i am new to this webite and looking for some advice.
im seventeen years old and recently found out i am pregnant. im excited but i had my first transvaginal u/s on 7/6/09 and there was a gestational sac but no heart beat. since my period is extremly irregular i am not sure when mt last period was. so my doctor estimated i was about six weeks. i have another u/s on 7/14/09. should i be worried?

any advice would be helpful please.

[sstaceyy]

6 wks is to early for a heart beat you wont hear a heart beat till 7-9 wks. you shouldnt worry every thing will be just fine

[Tanker Chic]

Nope you shouldn't worry.. even if you were sure you were 6wks, you may see a heart beat or you may not..  and if you aren't sure, that further increases the chance that you may not get a heart beat this early.  

Best of luck to you.. be a good mommy!!

[ammup]

my LMP was on March 1st.  I had an u/s done on april 22nd, which showed a sac but no heart beat.  further I had an u/s again on may 7, which again showed no heart beat.  this is my first pregnancy.  I am very much worried.  please advise.